Haggle for a year to get the agreement (6)
I believe the answer is:
treaty
'agreement' is the definition.
(treaty is a kind of agreement)
'haggle for a year to get the' is the wordplay.
'haggle for' becomes 'tre' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'year' becomes 'y'.
'to get' is a charade indicator (letters next to each other).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'y' after 't' is 'ty'.
'tre'+'a'+'ty'='TREATY'
Can you help me to learn more?
(Other definitions for treaty that I've seen before include "Formal agreement between states" , "Political or private agreement" , "Formal pact" , "A pact between countries" , "Covenant" .)