1: Articles by the uncentred Hazards - they usually indicate omissions (9)
3: Demonstrated the way in which to keep poles apart (5)
4: Yew chopped up inside close to January (3,4)
5: Got excited by unusual tulip (3,2)
6: Broadcast share in genuine show trial (9)
7: Defusing timer incorrectly can lead to this! (13)
8: Dizzy Ben is a playwright (5)
10: Tidy up and clean floor finally and decisively (4,3,3,3)
13: Father and mother's embracing Nora in pictures (9)
15: To Marx, it'd troubled an old printer? (3,6)
18: Clip of Southern Conservative is very revealing at first (7)
19: Splay out and make tremble (5)
20: Tendon's abnormal growth is in remission (5)
21: Large vessel is berthed in China or Taiwan (5)