Decorates gargoyle's face with glazes after head is lost (9)
I believe the answer is:
garnishes
'decorates' is the definition.
(garnishing is a kind of decorating)
'gargoyle's face with glazes after head is lost' is the wordplay.
'face' says to take the initial letters.
'with' is a charade indicator (letters next to each other).
'glazes' becomes 'varnishes'.
'after head is lost' means to remove the first letter.
The initial letter of 'gargoyle' is 'g'.
'varnishes' with its initial letter removed is 'arnishes'.
'g'+'arnishes'='GARNISHES'
(Other definitions for garnishes that I've seen before include "food additives?" , "dresses" .)