Rat briefly stopping near fish (8)
I believe the answer is:
stingray
'fish' is the definition.
(type of fish)
'rat briefly stopping near' is the wordplay.
'briefly' means to remove the last letter.
'stopping' means one lot of letters goes inside another (inserted letters stop or plug a gap).
'near' becomes 'stingy' (I've seen this before).
'rat' with its final letter removed is 'ra'.
'ra' put within 'stingy' is 'STINGRAY'.
(Other definitions for stingray that I've seen before include "TV show" , "menace in the water" , "Large fish with tail spine" , "Marine creature with venomous tail" , "Poisonous spined fish" .)