A professional needs new protective garment (5)
I believe the answer is:
apron
'protective garment' is the definition.
(apron is a kind of protective garment)
'a professional needs new' is the wordplay.
'professional' becomes 'pro' ('pro' can be a synonym of 'professional').
'needs' means one lot of letters go next to another.
'new' becomes 'n'.
'a'+'pro'+'n'='APRON'
(Other definitions for apron that I've seen before include "skirt" , "Airport area for manoeuvring and loading planes" , "Garment for protection" , "Put on to protect" , "Kitchen protector" .)