Advanced slowly, for the most part (4)
I believe the answer is:
lent
'advanced' is the definition.
(advance can mean to lend)
'slowly for the most part' is the wordplay.
'slowly' becomes 'lento' (musical instruction).
'for the most part' means to remove the last letter (most but not all of the letters).
'lento' with its last letter taken away is 'LENT'.
(Other definitions for lent that I've seen before include "days before Easter" , "Christian period of abstinence" , "Provided loans" , "Advanced" , "Christian penitential period" .)