Gay bishop, supple and graceful (6)
I believe the answer is:
blithe
'gay' is the definition.
(I've seen this before)
'bishop supple and graceful' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'supple and graceful' becomes 'lithe' (I've seen this before).
'b'+'lithe'='BLITHE'
(Other definitions for blithe that I've seen before include "Carefree and happy" , "Happy, without worries or cares" , "Uncaring" , "Gay" , "Innocently happy" .)