The expenditure needed to expose non-professional (6)
I believe the answer is:
outlay
'the expenditure' is the definition.
('outlay' can be a synonym of 'expenditure')
'to expose non-professional' is the wordplay.
'to expose' becomes 'out' (outing is a kind of exposing).
'non-professional' becomes 'lay' (I've seen this before).
'out'+'lay'='OUTLAY'
'needed' is the link.
(Other definitions for outlay that I've seen before include "Money needed upfront" , "Expenditure on something" , "Amount of money spent" , "Spending" , "Understood only by few" .)