Fish that may be straying (8)
I believe the answer is:
stingray
'fish' is the definition.
(stingray is a kind of fish)
'may be straying' is the wordplay.
'may be' indicates anagramming the letters.
'straying' with letters rearranged gives 'STINGRAY'.
'that' acts as a link.
(Other definitions for stingray that I've seen before include "Large fish with tail spine" , "TV show" , "Fish with venomous tail" , "Poisonous spined fish" , "menace in the water" .)