Head of school with rule for an audience (9)
I believe the answer is:
principal
'head of school' is the definition.
(I've seen this before)
'rule for an audience' is the wordplay.
'rule' becomes 'principle' (synonyms).
'for an audience' shows a homophone (sound like) (as the word might sound to an audience).
'principle' is a homophone of 'PRINCIPAL'.
'with' acts as a link.
(Other definitions for principal that I've seen before include "Source of income" , "Capital, or debt, on which interest is calculated" , "Cardinal" , "Main, leading" , "Chief, main" .)