Arbiter asking a criminal to agree on terms (6,1,7)
I believe the answer is:
strike a bargain
'agree on terms' is the definition.
'arbiter asking a criminal' is the wordplay.
'criminal' indicates anagramming the letters.
'arbiter'+'asking'+'a'='arbiteraskinga'
'arbiteraskinga' anagrammed gives 'STRIKE A BARGAIN'.
'to' is the link.
(Other definitions for strike a bargain that I've seen before include "reach an agreement" , "Settle" , "Make a deal" , "Agree on terms" , "succeed in arbitration?" .)