Squirm and wither, perhaps (6)
I believe the answer is:
writhe
'squirm' is the definition.
(synonyms)
'wither perhaps' is the wordplay.
'perhaps' indicates an anagram.
'wither' is an anagram of 'WRITHE'.
'and' is the link.
(Other definitions for writhe that I've seen before include "feel acute embarrassment" , "Thrash" , "Twist as in pain" , "worm" , "Twist in agony" .)