Fish appeared to be off (5)
I believe the answer is:
smelt
'fish' is the definition.
(I know that smelt is a type of fish)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for smelt that I've seen before include "were high" , "Small fish of salmon species" , "23 [FISH]" , "Food fish often fried" , "whiffed" .)