Standing on to put back the money (5)
I believe the answer is:
notes
'the money' is the definition.
(I've seen this before)
'standing on to put back' is the wordplay.
'standing' shows that the letters should be reversed in order (in a down clue, letters stand up).
'to put' becomes 'set' (both can mean to place or position).
'back' shows that the letters should be reversed in order.
'on' in reverse letter order is 'no'.
'set' in reverse letter order is 'tes'.
'no'+'tes'='NOTES'
(Other definitions for notes that I've seen before include "Pays attention" , "Sees" , "Marks on a stave" , "Memos; marks" , "eg E F G (mus.)" .)