Money for extra work done ahead of season (8)
I believe the answer is:
overtime
'money for extra work' is the definition.
(pay for work done outside of official hours)
'done ahead of season' is the wordplay.
'done' becomes 'over' (I've seen this before).
'ahead of' is a charade indicator (letters next to each other) (I've seen this in other clues).
'season' becomes 'time' (both can mean a period).
'over'+'time'='OVERTIME'
(Other definitions for overtime that I've seen before include "Extra hours worked" , "Work in excess of fixed period" , "Work beyond normal hours? Remove it" , "Pay for extra work" , "Work outside normal hours" .)