Announcement of top dog (4)
I believe the answer is:
peke
'dog' is the definition.
(short for Pekingese)
'announcement of top' is the wordplay.
'announcement of' shows a homophone (sound like).
'top' becomes 'peak' (synonyms).
'peak' sounds like 'PEKE'.
(Other definitions for peke that I've seen before include "5 [MANS BEST FRIEND]" , "Little dog" , "Snub-nosed lap-dog (colloq.)" , "Small snub-nosed dog" , "Breed of dog (shortened)" .)