Across:
1 Comical side (HUMOUR) seems missing from summerhouse (‘seems’ missing from ‘summerhouse’ = umhou = HUMOUR),
4 Uplifting (= reverse indicator) advantage (plus = S-ULP-) embodies cornerback in front of (‘Cornerback’ in front of = -C-) The Hill (-TOR) (SCULPTOR) – the one craftily talking lumps out of Rock (SCULPTOR),
9 Evil (MALIGN) Frenchman (M-) from line-up (line-up = -ALIGN) (MALIGN),
10 Regular (UNIFORM-) school (-S) (UNIFORMS) habits (UNIFORMS),
12 Father’s (POPE’S) offspring (son = NOS-) serves up (= reverse indicator) starter eaten (starter eaten = -E) (POPE’S NOSE) with piece of chicken (POPE’S NOSE),
13 Orchestral opening (‘Orchestral’ opening = O-) and rap (slap) backtrack (= reverse indicator) (slap = -PALS) (OPALS) produced by The Stones (OPALS),
14 Genial (GOOD-HUMOURED) boxer (dog) staggering back (= reverse indicator) (dog = GO-D) around ring (-O-) getting 1 across (‘humour’ = -HUMOUR-) on a fair amount of (half of) the lip (edge) (half of the ‘EDge’ = -ED) (GOOD-HUMOURED),
18 Maintain control (KEEP ONE’S COOL) of castle (KEEP) for individual (ONE-) going to school (school) without a second thought (‘second ‘tHought’ = h) (‘school’ without ‘h’ = -S COOL) (KEEP ONE’S COOL),
21 Detailed (t) aid to the puzzled (hint) (‘hint’ without ‘t’ = -HIN-) in California (CA = C-A) (CHINA), a large land mass that’s on the Pacific Ocean (CHINA),
22 Relative of 17 down (‘bluebell’ is in the lily family = LILY-) is leading chess player (-WHITE opens/leads in chess) (LILYWHITE) living in Kildare (LILYWHITE),
24 Incited a (incited a) riot (= anagram indicator) (incited a = INDICATE) for show (INDICATE),
25 Establish (CREATE) on the borders of Creole State (on the borders of ‘CREole stATE’ = CREATE),
26 Fresh (= anagram indicator) veneer (veneer = EVER-NE) covering yard (-Y-) means nothing (-O-) (EVERYONE) to the people in general (EVERYONE),
27 Poor (= anagram indicator) Dante (Dante = DENTA-) at the opening of Limbo (opening of ‘Limbo’ = -L) (DENTAL) provides description of various teething problems perhaps (DENTAL).
Down:
1 The first to be found on site (HOME PAGE) by The House (HOME) attendant (attendant/train-bearer = PAGE) (HOME PAGE),
2 Trim (e) guy (male) (‘male’ without ‘e’ = MAL-) is a (-A) rugby player (-PROP) (MALAPROP) incapable of stringing a proper sentence together (MALAPROP),
3 Puts pressure on (URGES) political movements (purges) to get rid of leader (p) (‘purges’ without ‘p’ = URGES),
5 Trick (CON-) unstable (= anagram indicator) Queen (queen = -EQUEN-) Cleopatra the Seventh (‘cleopaTra’ the seventh = -T-) into scheming (sly = -S-LY) (CONSEQUENTLY), as a result (CONSEQUENTLY),
6 Scraps (LEFTOVERS) with leaders of extended family triumphing (leaders of ‘Extended Family Triumphing’ = -EFT-) in Romeo and Juliet (lovers = L-OVERS) (LEFTOVERS),
7 There’s no mud in Dartmouth (there’s no ‘mud’ in ‘Dartmouth’ = artoth = THROAT) where you’ll find the frog? (in the THROAT),
8 Refuse to give in to (RESIST) bank’s research scientist (banks ‘RESearch scientIST’ = RESIST),
11 Cool local (COSMOPOLITAN) cocktail? (COSMOPOLITAN cocktail),
15 Brief (t) success (hit) (‘hit’ without ‘t’ = HI-) at archery (archery) confusing (= anagram indicator) (archery = -ERARCHY) (HIERARCHY) top people in organisation (HIERARCHY),
16 Gangster (Don = DO-N-) crossing road (-MI-) worker (-ANT) (DOMINANT) is not backward in coming forward (DOMINANT),
17 Part of Lily’s family (BLUEBELL) in Dublin (BLUEBELL),
19 Sprightly (ACTIVE) gran gets out of vintage car (‘gran’ gets out of ‘vintage car’ = vitaec = ACTIVE),
20 Doctor (FIDDLE) and theologian (Doctor of Divinity = -DD-) mentioned in case notes (FI-LE) (FIDDLE),
23 It’s inferior (WORSE) upsetting (= reverse indicator) difference of opinion (row = WOR-) from heartless (e) witness (see) (‘see’ without ‘e’ = -SE) (WORSE).