Row around river to find fish (5)
I believe the answer is:
sprat
'fish' is the definition.
(sprat is a kind of fish)
'row around river' is the wordplay.
'row' becomes 'spat' (spat is a kind of row).
'around' is an insertion indicator.
'river' becomes 'r'.
'spat' placed around 'r' is 'SPRAT'.
'to find' acts as a link.
(Other definitions for sprat that I've seen before include "Young herring" , "Jack --, non-fat eater" , "It may catch a mackerel" , "Herring's smaller relative" , "Small marine fish" .)