Some perch, a remarkable fish (4)
I believe the answer is:
char
'fish' is the definition.
(char is a kind of fish)
'some perch a remarkable' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'CHAR' can be found hidden inside 'perch a remarkable'.
(Other definitions for char that I've seen before include "Sear - fish" , "One cleans" , "Drink" , "'Mrs Mopp'" , "Noiseless" .)