Some film for which you need to pay on time (7)
I believe the answer is:
footage
'some film' is the definition.
(footage is a kind of film)
'to pay on time' is the wordplay.
'to pay' becomes 'foot' (as in footing the bill).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'time' becomes 'age' (an age is a period of time).
'foot'+'age'='FOOTAGE'
'for which you need' is the link.
(Other definitions for footage that I've seen before include "Piece of filmed material" , "amount of film" , "Quantity of film (of event)" , "quantity shot" , "Part of film" .)