Professional wearing article, protective garment (5)
I believe the answer is:
apron
'protective garment' is the definition.
(apron is a kind of protective garment)
'professional wearing article' is the wordplay.
'professional' becomes 'pro' ('pro' can be a synonym of 'professional').
'wearing' is an insertion indicator.
'article' becomes 'an' (indefinite article).
'pro' put within 'an' is 'APRON'.
(Other definitions for apron that I've seen before include "Put on to protect" , "Type of stage; pinny" , "Paved surface where aircraft stand when not in use" , "Cook's protector" , "Part of stage in front of the curtain" .)