Little Benjamin holds large fish (6)
I believe the answer is:
blenny
'fish' is the definition.
(blenny is a kind of fish)
'little benjamin holds large' is the wordplay.
'little' becomes 'l' (abbreviation).
'benjamin' becomes 'ben' (short for Benjamin).
'holds' indicates putting letters inside.
'large' becomes 'ny' (I am not sure about this - if you are sure you should believe this answer much more).
'l' placed inside 'ben' is 'blen'.
'blen'+'ny'='BLENNY'
Can you help me to learn more?
(Other definitions for blenny that I've seen before include "Spiny-finned fish" , "slimy fish" .)