Attempt to brew tea in formal agreement (6)
I believe the answer is:
treaty
'formal agreement' is the definition.
(I've seen this in another clue)
'attempt to brew tea in' is the wordplay.
'attempt' becomes 'try' (synonyms).
'to brew' is an anagram indicator.
'in' indicates putting letters inside.
'tea' with letters rearranged gives 'eat'.
'try' placed around 'eat' is 'TREATY'.
(Other definitions for treaty that I've seen before include "convention?" , "alliance" , "Formal agreement between states" , "Pact, accord between states" , "International agreement" .)