He has to pay the price of publicity (10)
I believe the answer is:
advertiser
'he has to pay the price' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'publicity' is the wordplay.
I cannot quite see how this works, but
'publicity' could be 'advert' (advert is a kind of publicity) and 'advert' is present in the answer.
The remaining letters 'iser' 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).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for advertiser that I've seen before include "He pushes" , "Publicist" , "One publicising a product (S, not Z)" , "Part of a newspaper's title" , "commercial employee" .)