Fish that's asleep (6)
I believe the answer is:
kipper
'fish' is the definition.
(type of fish)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for kipper that I've seen before include "has been caught napping" , "One smoked" , "part of breakfast?" , "One drops off" , "Smoked fish" .)