Surface echo absorbed by unusual nerve (6)
I believe the answer is:
veneer
'surface' is the definition.
(thesaurus)
'echo absorbed by unusual nerve' is the wordplay.
'echo' becomes 'e' (phonetic alphabet: alpha, bravo, charlie etc.).
'absorbed by' indicates putting letters inside.
'unusual' indicates an anagram.
'nerve' is an anagram of 'vener'.
'e' inserted into 'vener' is 'VENEER'.
(Other definitions for veneer that I've seen before include "A thin layer on the surface, often wood" , "Specious outward appearance of good quality" , "Face" , "Thin layer of wood or plastic" , "Thin superficial layer" .)