Thin and graceful (7)
(Other definitions for slender that I've seen before include "Gracefully thin and elegant" , "Ann Page's suitor" , "Svelte" , "Lean" , "Fine" .)
'thin and graceful' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lithe that I've seen before include "able to move supply" , "Able to move and bend gracefully" , "Don -, opera by Verdi" , "Loose-limbed" , "quick to move" .)