Sunday World Cryptic

[Bernie]

31a collision in the billiard room (6)?a????
22a place to become a beast(7)?????d?
Quick xword
16d degraded(6)
20a sickness (6) I have nausea which gives an a for2d letter of degraded
17d aver(6)?s????
Many thanks

[elliemay1]

17 assert

[mac44]

31a. cannon

[sedge47]

31a cannon

[mac44]

22a. polecat

[eanceoil]

21 cannon
22 polecat (place to anag)

[elliemay1]

16 abased??

[elliemay1]

16 demean or debase if clue is degrade??

[eanceoil]

fallen http://crosswordtracker.com/clue/degraded/ fits with this

[fiction-factory]

I think clue will probably be degraded as it's mentioned twice

[fiction-factory]

abject?

[eanceoil]

16d is nausea, the 1st letter a in nausea is the a in Fallen, the letters for degraded are ?a?l?n

[Jackdaw33]

17 assert

[eanceoil]

I meant, 20 across is nausea, 16d has the letters I typed above

[elliemay1]

Thank you for letting us know, eanceoil.

[eanceoil]

You're welcome elliemay1, my laptop crashed there for a few minutes - too many tabs on the go