Supple, flexible (6)
I believe the answer is:
I believe this clue is a double definition.
'supple' is the first definition.
(I know that supple can be written as limber)
'flexible' is the second definition.
(similar in meaning)
(Other definitions for limber that I've seen before include "Artillery equipment" , "Lithe" , "Able to move supply" , "Agile, supple" , "Supple; flexible" .)