For one fishing, nothing right in salmon river (6)
I believe the answer is:
osprey
'for one fishing' is the definition.
(bird which eats fish)
'nothing right in salmon river' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'right' becomes 'r' (common abbreviation).
'in' means one lot of letters goes inside another.
'salmon river' becomes 'spey' (River Spey in Scotland, known for its salmon).
'r' put into 'spey' is 'sprey'.
'o'+'sprey'='OSPREY'
(Other definitions for osprey that I've seen before include "Fish-eater" , "Fish-eating 15 ac" , "Spy roe (anag)" , "One flying" , "Large seabird" .)