Money once raised in late September (6)
I believe the answer is:
peseta
'money once' is the definition.
(former Spanish currency)
'raised in late september' is the wordplay.
'raised' is a reversal indicator (going up in a down clue).
'in' says the answer is hidden in the clue.
'atesep' is hidden within 'late september'.
'atesep' written backwards gives 'PESETA'.
(Other definitions for peseta that I've seen before include "Get ready once for Spain" , "Old Spanish currency" , "Old bit" , "Out of date bread" , "Old Spanish coin" .)