Trouper, playing loud man at National Theatre, leads in Zenda as "unconquered" villain (6,2,7)
I believe the answer is:
rupert of hentzau
'villain' is the definition.
I know nothing about this answer so I can't judge whether this works.
'trouper playing loud man at national theatre leads in zenda as unconquered' is the wordplay.
'playing' indicates an anagram.
'loud man at' becomes 'fhe' (I can't explain this - if you can you should give a lot more credence to this answer).
'national theatre' becomes 'NT' (abbreviation).
'leads in' indicates taking the first letters (I've seen 'lead in' mean this).
The initial letters of 'zenda as unconquered' is 'zau'.
'trouper' is an anagram of 'ruperto'.
'ruperto'+'fhe'+'nt'+'zau'='RUPERT OF HENTZAU'
Can you help me to learn more?
(Another definition for rupert of hentzau that I've seen is " literary hero".)