A fish little different from the roach (5)
I believe the answer is:
loach
'a fish' is the definition.
(loach is a kind of fish)
'little different from the roach' is the wordplay.
'little' becomes 'lo' (I am not sure about this - if you are sure you should believe this answer much more).
'different' becomes 'other' (similar in meaning).
'from' suggests deleting specific letters.
'the'+'roach'='theroach'
'theroach' with 'other' taken away is 'ach'.
'lo'+'ach'='LOACH'
Can you help me to learn more?
(Other definitions for loach that I've seen before include "Fish with barbels around mouth" , "Film-maker" , "Freshwater fish; rhymes with freshwater fish" , "Fish - British film director" , "River fish - film director" .)