It’s socially acceptable to be in debt at the start (5)
I believe the answer is:
debut
'the start' is the definition.
(debut is a kind of start)
'it's socially acceptable to be in debt' is the wordplay.
'it's socially acceptable' becomes 'u'.
'to be in' indicates putting letters inside.
'u' placed inside 'debt' is 'DEBUT'.
'at' acts as a link.
(Other definitions for debut that I've seen before include "First appearence as of society girl" , "Beginning, first performance" , "First appearance in society" , "Initial appearance" , "entrance" .)