1 Bit of plant in waste matter (4)
2 Mess up race I entered (4)
3 Hit the drink in part of London (9)
4 Annoy me over total number (6)
5 Write a small amount (3)
6 Crusoe, perhaps, getting bird numbers to go up (8)
7 Account from one cadet at sea (8)
11 DIY firm we use for delivery work? (9)
12 Rod Stewart at first also left seat (8)
13 One who plays first by ear, perhaps (8)
16 Run away getting key (6)
18 Quiet song for couple (4)
19 Strokes dogs, perhaps (4)
21 Bird found in some mudflats (3)