Free to get new skin (4)
I believe the answer is:
rind
'skin' is the definition.
(synonyms)
'free to get new' is the wordplay.
'free' becomes 'rid' (to be free of something is to be rid of it).
'to get' indicates putting letters inside.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'rid' enclosing 'n' is 'RIND'.
(Other definitions for rind that I've seen before include "Outer layer (of cheese)" , "Hard outer skin, of an orange say" , "tough skin" , "Outer edge of a bacon rasher" , "Outer skin of citrus fruit" .)