Sinuous snake sheds skin (5)
I believe the answer is:
lithe
'sinuous' is the definition.
(I know that sinuous can be written as lithe)
'snake sheds skin' is the wordplay.
'snake' becomes 'slither' (I've seen this before).
'sheds skin' says to take the centre (I've seen 'shedding skin' mean this (the word's 'skin' is removed)).
The central letters of 'slither' are 'LITHE'.
(Other definitions for lithe that I've seen before include "showing great athletic ability" , "flex with no difficulty" , "Loose-limbed" , "grace" , "Lissom, supple" .)