Location of a debutante's first gown (7)
I believe the answer is:
address
'location' is the definition.
(address is a kind of location)
'a debutante's first gown' is the wordplay.
'debutante's first' becomes 'd' (1st letter of 'debutante').
'gown' becomes 'dress' (gown is a kind of dress).
'a'+'d'+'dress'='ADDRESS'
'of' acts as a link.
(Other definitions for address that I've seen before include "Place where someone lives" , "Speak formally to an audience" , "One's designated location" , "Speak to at home?" , "In almost desperate straits" .)