Recoil, struggling to eat fish - a snapper? (9)
I believe the answer is:
crocodile
'a snapper?' is the definition.
(an animal which 'snaps')
'recoil struggling to eat fish' is the wordplay.
'struggling' indicates anagramming the letters.
'to eat' is an insertion indicator.
'fish' becomes 'cod' (type of fish).
'recoil' is an anagram of 'croile'.
'croile' placed around 'cod' is 'CROCODILE'.
(Other definitions for crocodile that I've seen before include "line of schoolkids?" , "Insincere show of sorrow" , "Reptile - line of schoolchildren" , "handbag material?" , "Large aquatic reptile" .)