1: I deem turds a regrettable necessity (11)
2: Three kernels of copper-yellow grain (3)
3: Hearing sis nose around (7)
4: Foreign car, in neutral, crashed (7)
5: Keep rolling and swelling, Doc! (7)
6: Grill when involved in corruption (5)
7: Odds of niece being born (3)
9: Check about a form of power (5)
11: Bouquet's sent up to network director? (5)
12: Lepers treated by North Dakota specialist? Brilliant! (11)
14: Start reorganizing notes (5)
16: Usher again in the audience for evidence of payment (7)
17: Links to some 7-down (5)
18: A grape drink for Edwin emptied inside (3,4)
19: Hard to define evil, use 'gone astray' (7)
20: German poet in anger tying up Kay (5)
21: Worthless even when recycled (3)