Determined to back, having money (5)
I believe the answer is:
notes
'money' is the definition.
(thesaurus)
'determined to back' is the wordplay.
'determined' becomes 'seton' (I've seen this before).
'to back' says the letters should be written in reverse.
'seton' in reverse letter order is 'NOTES'.
'having' acts as a link.
(Other definitions for notes that I've seen before include "registers?" , "Paper money" , "Sounds" , "Short written messages" , "Marks on a stave" .)