They seem singularly agreeable! (4)
I believe the answer is:
ayes
I'm afraid I can't explain this answer.
Can you help me to learn more?
(Other definitions for ayes that I've seen before include "The yes votes at committee meeting" , "Votes of approval during 5 Down" , "Sounds of agreement" , "The yes-votes at committee meeting" , "Affirmatives at sea" .)