Bonus promotion almost over (3-2)
I believe the answer is:
add-on
'bonus' is the definition.
(I've seen this in another clue)
'promotion almost over' is the wordplay.
'promotion' becomes 'ad' (short for advert).
'almost' means to remove the last letter (almost the whole word is kept).
'over' becomes 'done' (both can mean finished).
'done' with its final letter taken off is 'don'.
'ad'+'don'='ADD-ON'
(Other definitions for add-on that I've seen before include "Accessory device" , "Feature supplementing standard model" , "Extra bit" , "Extra peripheral item" , "Extra unit, peripheral" .)