Fish in wreck (7)
I believe the answer is:
torpedo
I believe this is a double definition.
'fish' is the first definition.
(torpedo is a kind of fish)
'wreck' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for torpedo that I've seen before include "fish you want" , "Trooped off with underwater missile" , "Poor Ted (anag)" , "To wreck" , "Destroy" .)