Form of betting -- cancel her bet, improperly written (6,6)
I believe the answer is:
treble chance
'form' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?
'betting cancel her bet improperly written' is the wordplay.
'cancel her bet' can be anagrammed to 'TREBLE CHANCE'.
Though, I am not clear how this is indicated.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for treble chance that I've seen before include "Form of football pool" , "that could make a fortune" , "pools" .)