1: Catch up before old crooner talking blather (7)
2: Chump getting past in chasm (5)
3: Norse gentleman? Not exactly. (5)
4: Frequently decimal? (5)
5: Fatal crime may lead to damnation (6,3)
6: Shell compensate for loss in certain risky starts (7)
7: Ultimately, dconstruire, to the French intellectual, is simple (9)
8: More stable, or slide around (7)
12: Poor Marist to freeze in cessation of hostilities (9)
13: Criticize changes heard in piano pieces (9)
14: Again design rose float (7)
15: Force of nature, like Chubby Checker (7)
16: Palestinian group participating in way out feat (7)
18: Face-off stopped and relieved the pressure (5)
19: Oriental talc dispenser deserves acclaim (5)
20: Trunk and tangled roots (5)