Still twenty required to get even (6,1,5)

'get even' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'still twenty required' is the wordplay.
I cannot quite understand how this works, but
'twenty' could be 'score' (synonyms) and 'score' is present in the answer.
'required' could be 'set' (as in a set text) and 'set' is found within the answer.
This may be the basis of the clue (or it may be nonsense).

'to' is the link.

Can you help me to learn more?