Prices of lettuce good man rejected (5)
I believe the answer is:
costs
'prices' is the definition.
('cost' can be a synonym of 'price')
'lettuce good man rejected' is the wordplay.
'lettuce' becomes 'cos' (cos lettuce is a kind of lettuce).
'good man' becomes 'st'.
'rejected' shows that the letters should be reversed in order.
'st' backwards is 'ts'.
'cos'+'ts'='COSTS'
'of' acts as a link.
(Other definitions for costs that I've seen before include "Overheads" , "Legal expenses" , "Damages" , "Expenditures, outlays" , "prices" .)