Agree to change, being keen (5)
I believe the answer is:
eager
'keen' is the definition.
(thesaurus)
'agree to change' is the wordplay.
'to change' indicates anagramming the letters.
'agree' with letters rearranged gives 'EAGER'.
'being' acts as a link.
(Other definitions for eager that I've seen before include "Like some beavers" , "Ardent" , "Swiss mountain" , "It's a bore" , "passionate" .)