501 advanced into pub, heading for alcoholic state (7)
I believe the answer is:
indiana
'state' is the definition.
(US state)
'501 advanced into pub heading for alcoholic' is the wordplay.
'50i' becomes 'di' (50i in Roman numerals).
'advanced' becomes 'a' (abbreviation).
'into' is an insertion indicator.
'pub' becomes 'inn' (an inn is a type of pub).
'heading for' indicates taking the first letters.
The initial letter of 'alcoholic' is 'a'.
'di'+'a'='dia'
'dia' going within 'inn' is 'indian'.
'indian'+'a'='INDIANA'
(Other definitions for indiana that I've seen before include "___ Jones, Harrison Ford hero - US state" , "Gary's place" , "member of 2 [THE STATES]" , "--- Jones, Harrison Ford film character" , "Vice President Pence's state" .)