Otherwise a Conservative's rhetoric (7)
I believe the answer is:
oratory
'rhetoric' is the definition.
(both can mean formal speech)
'otherwise a conservative's' is the wordplay.
'otherwise' becomes 'or'.
'conservative' becomes 'tory' (informal term for a Conservative Party member).
'or'+'a'+'tory'='ORATORY'
(Other definitions for oratory that I've seen before include "church" , "Formal speech-making, could be pompous" , "Art or skill of public speaking" , "devotional space" , "Place for private prayer" .)