Wriggle, squirm (6)
I believe the answer is:
writhe
I believe this clue is a double definition.
'wriggle' is the first definition.
(I know that wriggle can be written as writhe)
'squirm' is the second definition.
(synonyms)
(Other definitions for writhe that I've seen before include "worm" , "Wriggle" , "Twist as in pain" , "6, maybe in agony" , "Twist in agony" .)