Seven eels chopped up for snack (9)
I believe the answer is:
elevenses
'for snack' is the definition.
(I've seen this before)
'seven eels chopped up' is the wordplay.
'chopped up' indicates an anagram.
'seven'+'eels'='seveneels'
'seveneels' anagrammed gives 'ELEVENSES'.
(Other definitions for elevenses that I've seen before include "Soccer teams" , "Morning snack" , "Refreshments" , "Mid-morning snack" , "Mid-morning break" .)