The Sunday Crossword No 2996, Sunday 20 May 2018

ACROSS
1   Warning from revolutionary work in middle of argument (3-3) TIP-OFF {TI{OP<=}FF}
4   What about politician with a muscular movement being decisive? (8) EMPHATIC {E{MP}H}{A}{TIC}
10 Time after time entering bar and beginning to yell angrily (7) RATTILY {RA{T}{T}IL}{Yell}
11 Begin to deal with commercial outfit (7) ADDRESS {AD}{DRESS}
12 Peevish, right away, making tiny sum of money (3) SOU SOUr
13 Dry joke initially in exclusive story left by popular composer (5,6) SCOTT JOPLIN {SCO{TT}{Joke}OP}{L}{IN}
14 Small item of kit assembled, including a prong and energy socket (7,6)  MATINEE JACKET {A}{TINE}{E}{JACK} in {MET}

17 Shiny material in heap later shifted outside shelter (6,7) PATENT LEATHER {HEAP+LATER}* over {TENT}
21 Protective curtain, very large, left in artist's possession (8,3) MOSQUITO NET {OS}QUIT} in {MONET}
23 Business with black swan (3) COB {CO}{B}
24 Note less than clean (7) LAUNDER {LA}{UNDER}
25 Piece of mosaic put back before start of study period (7) TESSERA {SET<=}{St..y}{ERA}
26 Basic structure half of sketch revealed (8) SKELETON {SKEtch}{LET ON}
27 Loose-fitting garment working, I see, in a different way (6) ONESIE {ON}{I+SEE}*

By Jacek Rużyczka - Own work, CC BY-SA 3.0, Link

DOWN
1   Abnormal rise in volume that's annoying (8) TIRESOME {T{RISE*}OME}
2   Offend astute pro improperly forced into retirement (3,3,2,7) PUT OUT TO PASTURE  {PUT OUT} {ASTUTE+PRO}*
3   Is child following father? That must be a thrill (7) FRISSON {FR}{IS}{SON}
5   Indicated nitrogen in substance (5) MEANT {MEA{N}T}
6   Fish received on wharf (7) HADDOCK {HAD}{DOCK}
7   Struggling to help sect, think things are getting complicated (3,4,8) THE PLOT THICKENS*
8   Nothing wrong in church function (6) COSINE {C{O}{SIN}E}
9   Colour around unknown part of Alpine region (8) TYROLEAN {T{Y}{ROLE}AN}
15 Glen that gets spoilt eventually (2,6) AT LENGTH*
16 Game in enclosure disrupted by band? Not on (8) CRIBBAGE {C{RIBBon}AGE}
18 New deal excluding filling in actual roll (7) TRUNDLE {TRU{N}{DeaL}E}
19 Skilled worker, prejudiced, quietly dismissed (7) ARTISAN pARTISAN
20 One in climbing small trees showing signs of happiness (6) SMILES {S}{EL{1}MS}<=
22 Trunk carried by visitor sometimes (5) TORSO [T]

GRID