Adult favouring wearing long apron (8)
I believe the answer is:
pinafore
'apron' is the definition.
(thesaurus)
'adult favouring wearing long' is the wordplay.
'adult' becomes 'a'.
'favouring' becomes 'for' (I've seen this before).
'wearing' indicates putting letters inside.
'long' becomes 'pine' ('pine' can be a synonym of 'long'**).
'a'+'for'='afor'
'afor' placed inside 'pine' is 'PINAFORE'.
(Other definitions for pinafore that I've seen before include "Gilbert & Sullivan operetta 'HMS ........'" , "G&S ship" , "Musical craft" , "Apron-like garment" , "HMS -- (G&S)" .)