Bill on equality puts both leaders off, in fact (9)
I believe the answer is:
actuality
'fact' is the definition.
(thesaurus)
'bill on equality puts both leaders off' is the wordplay.
I cannot quite see how this works, but
'bill' could be 'act' (I've seen this in other clues) and 'act' is found within the answer.
'both' could be 't' (I've seen this in other clues) and 't' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Another definition for actuality that I've seen is " State of real existence".)