Fish joint (5)
I believe the answer is:
roach
I believe this is a double definition.
'fish' is the first definition.
(roach is a kind of fish)
'joint' is the second definition.
(thesaurus)
(Other definitions for roach that I've seen before include "Freshwatwer fish" , "Fresh-water food fish" , "Silver and red freshwater fish" , "Swimmer" , "Fish - part of a cannabis cigarette" .)