Lid securing head of raw fish (4)
I believe the answer is:
carp
'fish' is the definition.
(carp is a kind of fish)
'lid securing head of raw' is the wordplay.
'lid' becomes 'cap' (I've seen this in another clue).
'securing' indicates putting letters inside.
'head of' suggests taking the first letters.
The first letter of 'raw' is 'r'.
'cap' enclosing 'r' is 'CARP'.
(Other definitions for carp that I've seen before include "Fish < and beef" , "Nagging fish?" , "Complain like goldfish" , "Pond fish" , "Fish; nag pettily" .)