Twisted point supported by witticism (4)
I believe the answer is:
spun
'twisted' is the definition.
(spinning is a kind of twisting)
'point supported by witticism' is the wordplay.
'point' becomes 's' (S is an example).
'supported by' means one lot of letters go next to another (letters go below - in down clue).
'witticism' becomes 'pun' (pun is a kind of witticism).
's'+'pun'='SPUN'
(Other definitions for spun that I've seen before include "As yarn or silk may be" , "Was web" , "Twirled" , "Rotated cricket-ball" , "(Of cotton/wool) twisted into threads" .)