Looks at a key agreement (4)
I believe the answer is:
eyes
'looks at' is the definition.
(I've seen this before)
'a key agreement' is the wordplay.
'a key' becomes 'e' (I've seen this in other clues).
'agreement' becomes 'yes' (saying yes to something).
'e'+'yes'='EYES'
(Other definitions for eyes that I've seen before include "They look" , "Witnesses" , "Parts of needles" , "''Drink to me only with thine ...'' (Johnson)" , "They have pupils" .)