One dealing with worsening cough? (8)
I believe the answer is:
croupier
'one dealing with worsening cough?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'one' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
The remaining letters 'crouper' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for croupier that I've seen before include "rakes in the money" , "Person in charge of gambling-table" , "Manager of a gambling table" , "I procure (anag.)" , "Leisure worker" .)