Senior party on the money in Tokyo (5)
I believe the answer is:
doyen
'senior' is the definition.
(I've seen this before)
'party on the money in tokyo' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'on' is a charade indicator (letters next to each other).
'the money in tokyo' becomes 'yen' (I've seen this before).
'do'+'yen'='DOYEN'
(Other definitions for doyen that I've seen before include "Senior male member of a group" , "Prominent person in a particular field" , "Senior male figure in a profession" , "Respected expert" , "Prominent group member" .)