Challenger's profit given to teller (9)
I believe the answer is:
gainsayer
'teller' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see an association between them that I don't see?
'challenger's profit given' is the wordplay.
'challenger's' becomes 'sayer' (I am not sure about this - if you are sure you should believe this answer much more).
'profit' becomes 'gain' (synonyms).
'given' says to put letters next to each other.
'sayer' after 'gain' is 'GAINSAYER'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for gainsayer that I've seen before include "Person who denies" , "One contradicting" , "One who contradicts" .)