An expert included as protection (5)
I believe the answer is:
apron
'protection' is the definition.
(protective garment)
'an expert included' is the wordplay.
'expert' becomes 'pro' (short for professional).
'included' means one lot of letters goes inside another.
'an' enclosing 'pro' is 'APRON'.
'as' is the link.
(Other definitions for apron that I've seen before include "item of clothing in the kitchen" , "item of protective clothing" , "Kitchen protector" , "Protective garment - type of stage" , "Kitchen garment or aerodrome strip" .)