Will be right back - out getting fish (5)
I believe the answer is:
trout
'fish' is the definition.
(trout is a kind of fish)
'will be right back out' is the wordplay.
'will' means one lot of letters go next to another (I've seen this in other clues).
'be right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'back' is a reversal indicator.
'rt' backwards is 'tr'.
'tr' next to 'out' is 'TROUT'.
'getting' acts as a link.
(Other definitions for trout that I've seen before include "Small salmonlike fish" , "Tasty fish, perhaps of rainbow kind" , "Fish (associated with Schubert?)" , "Schubert work; fish" , "Tasty fish, brown or rainbow" .)