Revealed non-professional expenditure (6)
I believe the answer is:
outlay
'expenditure' is the definition.
(synonyms)
'revealed non-professional' is the wordplay.
'revealed' becomes 'out' (I've seen this in other clues).
'non-professional' becomes 'lay' (I've seen this before).
'out'+'lay'='OUTLAY'
(Other definitions for outlay that I've seen before include "Amount spent on something" , "Expenditure of money" , "Disbursement" , "cost" , "Money needed upfront" .)