Braggart's showy entrance (9)
I believe the answer is:
loudmouth
'braggart's' is the definition.
(I've seen this before)
'showy entrance' is the wordplay.
'showy' becomes 'loud' (both can mean ostentatious).
'entrance' becomes 'mouth' (eg the mouth of a cave).
'loud'+'mouth'='LOUDMOUTH'
(Other definitions for loudmouth that I've seen before include "Pistol, for example" , "One who causes trouble by speaking indiscreetly" , "noisy type" , "Braggart" , "Blowhard" .)