Someone who sells fish turned over a kipper? (7)
I believe the answer is:
sleeper
This might be a double definition.
'someone who sells fish turned' is the first definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'a kipper?' is the second definition.
(I've seen this before)
'over' acts as a link.
Can you help me to learn more?
(Other definitions for sleeper that I've seen before include "Brace to support rail on track" , "provide on-line support?" , "Somnolent person or beam under railway track" , "Train with berths" , "Inactive spy" .)