He has seniority and will perform for money (5)
I believe the answer is:
doyen
'he has seniority and will' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'perform for money' is the wordplay.
'perform' becomes 'do' (synonyms).
'for' means one lot of letters go next to another.
'money' becomes 'yen' (Japanese currency).
'do'+'yen'='DOYEN'
Can you help me to learn more?
(Other definitions for doyen that I've seen before include "Senior member of a profession or academy" , "Senior practitioner" , "Top expert in a field" , "Senior male figure in a profession" , "Grand old man" .)