May perhaps squirm on the inside (5)
I believe the answer is:
month
'may perhaps' is the definition.
(may is a kind of month)
'squirm on the inside' is the wordplay.
'inside' says the answer is hidden in the clue.
'MONTH' is hidden within 'squirm on the'.
(Other definitions for month that I've seen before include "Four-week period" , "Moon's period" , "Eg, February" , "December, say" , "See 10" .)