Bet, informally, that note dates from before 2002 (4)
I believe the answer is:
punt
'bet' is the definition.
(I know that punt is a more specific form of the action bet)
'informally that note dates from before 2002' is the wordplay.
I cannot really understand how this works, but
'note' could be 'n' (abbreviation) and 'n' is located in the answer.
The remaining letters 'put' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for punt that I've seen before include "Stake" , "risky affair" , "Pole-propelled boat" , "Riverboat" , "Flat boat or familiar currency" .)