Salmon is a hit with viewer (7)
I believe the answer is:
sockeye
'salmon' is the definition.
(I know that sockeye is a type of salmon)
'a hit with viewer' is the wordplay.
'a hit' becomes 'sock' (I've seen this in another clue).
'with' is a charade indicator (letters next to each other).
'viewer' becomes 'eye' (organ which sees or views).
'sock'+'eye'='SOCKEYE'
'is' is the link.
(Other definitions for sockeye that I've seen before include "Swimmer" , "Blue-backed salmon" , "Commercially important salmon" , "Type of Pacific salmon" , "Breed of salmon" .)