Set up newspaper? Something fishy here (3)
I believe the answer is:
gar
'something fishy here' is the definition.
(type of fish)
'set up newspaper?' is the wordplay.
'set up' says the letters should be written in reverse (in a down clue, letters go up).
'newspaper?' becomes 'rag' (informal term for a newspaper).
'rag' in reverse letter order is 'GAR'.
(Other definitions for gar that I've seen before include "something fishy here" , "Type of fish" , "Pike-like fish" , "Creature" , "swimmer" .)