A rod for freshwater fish (5)
I believe the answer is:
perch
I believe this is a double definition.
'a rod' is the first definition.
('perch' can be a synonym of 'rod')
'freshwater fish' is the second definition.
(perch is a kind of freshwater fish)
'for' is the link.
(Other definitions for perch that I've seen before include "[SOMETHING FISHY]" , "Rest (as a bird)" , "old measure of land" , "bird comes down on" , "Fish and imperial measure" .)