Graceful bird showing off, not half (4)
I believe the answer is:
swan
'graceful bird' is the definition.
(I've seen this before)
'showing off not half' is the wordplay.
'showing off' becomes 'swanking' ('swank' can be a synonym of 'show off').
'not half' suggests halving the letters.
'swanking' with half the letters taken is 'SWAN'.
(Other definitions for swan that I've seen before include "Whooper or trumpeter?" , "The Ugly Duckling's outcome" , "Large water bird" , "Mute, whooper or Bewick's bird" , "Graceful bird" .)