Beauty but skin deep (6)
I believe the answer is:
veneer
'skin deep' is the definition.
'veneer' can be an answer for 'skin' (thesaurus). I'm not sure about the 'deep' bit.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for veneer that I've seen before include "Thin wooden covering" , "Thin layer of a fine material on the surface" , "Superficial coating" , "Superficial shine" , "Thin decorative covering of fine wood" .)