Lissome, supple (5)
I believe the answer is:
lithe
I believe this clue is a double definition.
'lissome' is the first definition.
(I know that lissome can be written as lithe)
'supple' is the second definition.
(I know that supple can be written as lithe)
(Other definitions for lithe that I've seen before include "Physically flexible or supple" , "Able to move and bend gracefully" , "grace" , "Moving and bending with ease" , "Physically supple, agile" .)