Determined to put up money? (5)
I believe the answer is:
notes
'money?' is the definition.
(I know this)
'determined to put up' is the wordplay.
'determined' becomes 'set on' (I've seen this in another clue).
'to put up' is a reversal indicator.
'seton' written backwards gives 'NOTES'.
(Other definitions for notes that I've seen before include "fivers?" , "Observes; short comments" , "Memoranda" , "Takes into account" , "Pays attention" .)