Current agreement is unsurpassed (5)
I believe the answer is:
ideal
'unsurpassed' is the definition.
'current agreement' is the wordplay.
'current' becomes 'i' (symbol for electric current).
'agreement' becomes 'deal' (deal is a kind of agreement).
'i'+'deal'='IDEAL'
'is' acts as a link.
(Other definitions for ideal that I've seen before include "Just perfect, couldn't be better" , "without a flaw" , "Quite perfect, can't be improved on" , "The best conceivable" , "Cutting/stabbing weapons" .)