Made announcement about headmaster (4)
I believe the answer is:
dean
'headmaster' is the definition.
(thesaurus)
'made announcement about' is the wordplay.
'about' indicates the answer is hidden within the clue (the clue goes around or about the answer).
'DEAN' is hidden within 'made announcement'.
(Other definitions for dean that I've seen before include "University officer" , "Small valley - cathedral dignitary" , "Ice dancer" , "Jonathan Swift's occupation" , "Torvill's ice dancing partner" .)