Have a party, say (9)
I believe the answer is:
celebrate
'have a party say' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for celebrate that I've seen before include "Honour; make famous" , "Commemorate or eulogise" , "Put out the flags" , "Have a party to mark a happy event" , "Have festivity for special day or occasion" .)