Nobleman defaced jewel (4)
I believe the answer is:
earl
'nobleman' is the definition.
(member of the nobility)
'defaced jewel' is the wordplay.
'defaced' means to remove the first letter (the word with its face removed).
'jewel' becomes 'pearl' (pearl is a kind of jewel).
'pearl' with its initial letter taken off is 'EARL'.
(Other definitions for earl that I've seen before include "... Grey, fragrant Oriental tea" , "Sandwich perhaps" , "-- Grey, PM 1830-34" , "Male equivalent of a countess" , "A real titled lord" .)