They make open admissions at the theatre, etc. (5)
I believe the answer is:
doors
'they' is the definition.
Both the answer and definition are plural nouns.
Perhaps you can see an association between them that I don't see?
'make open admissions at the theatre etc' is the wordplay.
I cannot really see how this works, but
'make' could be 'do' (do can mean to make or prepare) and 'do' is present in the answer.
'theatre' could be 'or' (OR for Operating Room - surgical theatre) and 'or' is located in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for doors that I've seen before include "Ways in and out" , "Entrance barriers" , "Swinging or sliding barriers" , "Portals" , "Openings" .)