Keeping an audience in a repository (10)
I believe the answer is:
storehouse
'repository' is the definition.
(I know that storehouse is a type of repository)
'keeping an audience' is the wordplay.
'keeping an' becomes 'store' (I can't explain this - if you can you should give a lot more credence to this answer).
'audience' becomes 'house' (term for a theatre's audience).
'store'+'house'='STOREHOUSE'
'in a' acts as a link.
Can you help me to learn more?
(Other definitions for storehouse that I've seen before include "Depository" , "vault" .)