Fish novice kept in hat (7)
I believe the answer is:
bloater
'fish' is the definition.
(bloater is a kind of fish)
'novice kept in hat' is the wordplay.
I cannot quite understand how this works, but
'novice' could be 'l' (as in a learner driver with L-plates on their car) and 'l' is present in the answer.
'hat' could be 'boater' (boater is a kind of hat) and 'boater' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bloater that I've seen before include "Partially dried herring" , "Herring salted and smoked" , "Fish" , "that will more than fill one up" , "Buckling" .)