In favour of wearing a new pinafore? (5)
I believe the answer is:
apron
'pinafore?' is the definition.
(thesaurus)
'in favour of wearing a new' is the wordplay.
'in favour of' becomes 'pro' (I've seen this before).
'wearing' indicates putting letters inside.
'a new' becomes 'an' (I've seen this in other clues).
'pro' placed within 'an' is 'APRON'.
(Other definitions for apron that I've seen before include "edge" , "Kitchen garment or airfield area" , "Aircraft parking area" , "Projecting stage" , "Protective garment worn at front" .)