Stank of fish (5)
I believe the answer is:
smelt
I believe this clue is a double definition.
'stank' is the first definition.
(I've seen this before)
'fish' is the second definition.
(smelt is a kind of fish)
'of' acts as a link.
(Other definitions for smelt that I've seen before include "humming" , "sensed as fishy?" , "was whiffy" , "Produce metal by heat" , "Savoured" .)