Garden party’s destiny announced (4)
I believe the answer is:
fete
'garden party's' is the definition.
(I've seen this before)
'destiny announced' is the wordplay.
'destiny' becomes 'fate' (synonyms).
'announced' shows a homophone (sound like).
'fate' sounds like 'FETE'.
(Other definitions for fete that I've seen before include "Village event" , "Celebrate; village fair" , "Outdoor entertainment and sale, often for charity" , "Fund-raising function; festival" , "Wine and dine" .)