Advance unaccompanied, according to report (4)
I believe the answer is:
loan
'advance' is the definition.
(an advance is a loan)
'unaccompanied according to report' is the wordplay.
'unaccompanied' becomes 'lone' (on one's own).
'according to report' indicates a 'sounds like' (homophone) clue.
'lone' is a homophone of 'LOAN'.
(Other definitions for loan that I've seen before include "Something borrowed" , "Money borrowed; lend" , "temporary payment" , "Advance (money)" , "Temporary provision of money" .)