Guy changing quietly into black gown (4)
I believe the answer is:
robe
'gown' is the definition.
(synonyms)
'guy changing quietly into black' is the wordplay.
I cannot really see how this works, but
'black' could be 'b' (as in pencil classifications) and 'b' is found in the answer.
The remaining letters 'roe' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for robe that I've seen before include "Long loose garment or dressing gown" , "Ceremonial garb" , "Dressed buffalo hide" , "Formal vestment" , "Old cloak for Boer" .)