Fish which might be straying (8)
I believe the answer is:
stingray
'fish' is the definition.
(stingray is a kind of fish)
'might be straying' is the wordplay.
'might' indicates anagramming the letters (I've seen this in other clues).
'straying' with letters rearranged gives 'STINGRAY'.
'which' acts as a link.
(Other definitions for stingray that I've seen before include "Marine creature with venomous tail" , "Flatfish with barbed spine" , "Poisonous spined fish" , "Large fish with tail spine" , "Fish with venomous tail" .)