Payment not initially for one man-hour worked (10)
I believe the answer is:
honorarium
'payment' is the definition.
(honorarium is a kind of payment)
'not initially for one man-hour worked' is the wordplay.
'not initially' means to remove the first letter.
'one' becomes 'i' (Roman numeral).
'worked' indicates anagramming the letters.
'for'+'i'+'man'+'hour'='forimanhour'
'forimanhour' with its initial letter removed is 'orimanhour'.
'orimanhour' anagrammed gives 'HONORARIUM'.
(Another definition for honorarium that I've seen is " Nominal payment for professional services".)