Ring a theatre company set up to produce musical drama (5)
I believe the answer is:
opera
'musical drama' is the definition.
(I've seen this before)
'ring a theatre company set up' is the wordplay.
'ring' becomes 'o'.
'theatre company' becomes 'rep' (short for 'repertory theatre').
'set up' is a reversal indicator.
'a'+'rep'='arep'
'arep' reversed gives 'pera'.
'o'+'pera'='OPERA'
'to produce' is the link.
(Other definitions for opera that I've seen before include "Dramatic genre" , "musical performance" , "Falstaff, say" , "Form of theatre" , "Don Giovanni, for instance" .)