One sleeping like a fish? (6)
I believe the answer is:
kipper
'fish?' is the definition.
(type of fish)
'one sleeping like a' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for kipper that I've seen before include "Dried and smoked herring" , "One drops off" , "One not awake" , "has been caught napping" , "(Fishy) type of tie" .)