Professional wears a new pinafore (5)
I believe the answer is:
'pinafore' is the definition.
(I've seen this in another clue)
'professional wears a new' is the wordplay.
'professional' becomes 'pro' (synonyms).
'wears' indicates putting letters inside.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'pro' put within 'an' is 'APRON'.
(Other definitions for apron that I've seen before include "Protective kitchen wear", "Domestic protection", "Kitchen garment or aerodrome strip", "Pinafore", "area in front of aircraft hangar".)