Cinema worker in uniform reset the reels (9)
I believe the answer is:
usherette
'reset the reels' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'cinema worker in uniform' is the wordplay.
'cinema worker' becomes 'usher' (I've seen this in another clue).
'in uniform' becomes 'ette' (I can't justify this - if you can you should give a lot more credence to this answer).
'usher'+'ette'='USHERETTE'
Can you help me to learn more?
(Other definitions for usherette that I've seen before include "Girl guide" , "Person showing people to their seats" , "Cinema employee" , "Lady who shows you to your seat in cinema or theatre" , "She shows people to seats" .)