Doctor close to pay agreement (6)
I believe the answer is:
treaty
'agreement' is the definition.
(I know that agreement can be written as treaty)
'doctor close to pay' is the wordplay.
'doctor close' becomes 'y' (I can't justify this - if you can you should give a lot more credence to this answer).
'to' says to put letters next to each other (I've seen this in other clues).
'pay' becomes 'treat' (I've seen this in another clue).
'y' put after 'treat' is 'TREATY'.
Can you help me to learn more?
(Other definitions for treaty that I've seen before include "Contract between states" , "Formal agreement between two or more countries" , "Contract, pact" , "Formal agreement between nations" , "Political or private agreement" .)