That skin-deep beauty (6)
I believe the answer is:
veneer
'that skin' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for veneer that I've seen before include "A thin layer on the surface, often wood" , "Thin coating on the outside" , "Thin layer glued to a surface" , "Superficial polish" , "Thin covering of fine wood on a coarser one" .)