Singleton picked up person making advances (6)
I believe the answer is:
loaner
'person making advances' is the definition.
(someone giving out loans or advances)
'singleton picked up' is the wordplay.
'singleton' becomes 'loner' (a single person).
'picked up' shows a homophone (sound like).
'loner' is a homophone of 'LOANER'.
(Other definitions for loaner that I've seen before include "One providing cash" , "sort of banker?" , "public library, say?" .)