He's competing against, in something to do with money (9)
I believe the answer is:
contender
'he's competing against in something' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'do with money' is the wordplay.
'do' becomes 'con' (both can mean to defraud).
'with' means one lot of letters go next to another.
'money' becomes 'tender' (I've seen this before).
'con'+'tender'='CONTENDER'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for contender that I've seen before include "One seeking title" , "Struggler in rivalry" , "Competitor, challenger" , "One who strives" , "One engaged in a struggle" .)