Mean to consume mostly fresh fish (8)
I believe the answer is:
stingray
'fish' is the definition.
(stingray is a kind of fish)
'mean to consume mostly fresh' is the wordplay.
'mean' becomes 'stingy' ('stingy' can be similar in meaning to 'mean'**).
'to consume' means one lot of letters goes inside another.
'mostly' means to remove the last letter.
'fresh' becomes 'raw'.
'raw' with its final letter taken off is 'ra'.
'stingy' placed around 'ra' is 'STINGRAY'.
(Other definitions for stingray that I've seen before include "Dangerous fish" , "swimmer" , "Large venomous fish -- it's angry (anag)" , "menace in the water" , "Poisonous spined fish" .)