Payment securing a track lifted for film (7)
I believe the answer is:
feature
'payment' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'securing a track lifted for film' is the wordplay.
'securing' means one lot of letters goes inside another.
'track' becomes 'rut' (rut is a kind of track).
'lifted' shows that the letters should be reversed in order (going up in down clue).
'for film' becomes 'fee' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rut' reversed gives 'tur'.
'a'+'tur'='atur'
'atur' put inside 'fee' is 'FEATURE'.
(Other definitions for feature that I've seen before include "Special attraction" , "Characteristic" , "Newspaper article" , "Aspect; play a part" , "Focal point" .)