Beak gets happy posy (7)
I believe the answer is:
nosegay
'posy' is the definition.
(I know that posy can be written as nosegay)
'beak gets happy' is the wordplay.
'beak' becomes 'nose' (I've seen this in another clue).
'gets' is a charade indicator (letters next to each other).
'happy' becomes 'gay' (similar in meaning).
'nose'+'gay'='NOSEGAY'
(Other definitions for nosegay that I've seen before include "bunch of pansies?" , "Floral offering" , "spray" , "Fragrant bunch of flowers" , "Gone, say (anag)" .)