Simon said strange acknowledgement (9)
I believe the answer is:
admission
'acknowledgement' is the definition.
(admission is a kind of acknowledgement)
'simon said strange' is the wordplay.
'strange' is an anagram indicator.
'simon'+'said'='simonsaid'
'simonsaid' with letters rearranged gives 'ADMISSION'.
(Other definitions for admission that I've seen before include "The price of entry" , "Ticket holders expect this" , "Acknowledgement < of entry" , "Letting in - letting out" , "Anything conceded" .)