Fish reeked (5)
I believe the answer is:
smelt
This clue is a double definition.
'fish' is the first definition.
(I know that smelt is a type of fish)
'reeked' is the second definition.
(to reek is to smell very bad)
(Other definitions for smelt that I've seen before include "was whiffy" , "23 [FISH]" , "was off, we may deduce?" , "Extract (metal) from ore by heat" , "Extract metal from ore, fish" .)