They all agree it's easy to change (4)
I believe the answer is:
ayes
'they all agree' is the definition.
I know nothing about this answer so I can't tell whether this works.
'easy to change' is the wordplay.
'to change' indicates an anagram.
'easy' anagrammed gives 'AYES'.
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for ayes that I've seen before include "Sounds of agreement" , "Votes of approval during 5 Down" , "The yes votes at committee meeting" , "Votes in favour" , "Nautical positive responses" .)