Canvasses bringing up fish (5)
I believe the answer is:
sprat
'fish' is the definition.
(I know that sprat is a type of herring)
'canvasses bringing up' is the wordplay.
'canvasses' becomes 'tarps' (tarp is a kind of canvass).
'bringing up' says the letters should be written in reverse (I've seen 'brought up' mean this (in a down clue, letters go up)).
'tarps' written backwards gives 'SPRAT'.
(Other definitions for sprat that I've seen before include "Small fish, sardine, say" , "Small herring-like fish" , "'Set a . . . . . to catch a whale'" , "Small edible fish" , "little fish" .)