Supple, limber (5)
I believe the answer is:
lithe
I believe this is a double definition.
'supple' is the first definition.
(I know that supple can be written as lithe)
'limber' is the second definition.
(I've seen this before)
(Other definitions for lithe that I've seen before include "quick to move" , "Lissome, supple" , "Able to move and bend gracefully" , "Physically supple, agile" , "Not inflexible" .)