Expenditure revealed by non-professional (6)
I believe the answer is:
outlay
'expenditure' is the definition.
('outlay' can be a synonym of 'expenditure')
'revealed by non-professional' is the wordplay.
'revealed' becomes 'out' (I've seen this in other clues).
'by' is a charade indicator (letters next to each other).
'non-professional' becomes 'lay' (I've seen this before).
'out'+'lay'='OUTLAY'
(Other definitions for outlay that I've seen before include "Initial expense" , "What it costs" , "Expenditure on something" , "Disbursement" , "Amount of money spent" .)