Agreement sounds very full (4)

I believe the answer is:

pact

I'm a little stuck... Click here to teach me more about this clue!

'agreement' is the definition.
(a pact is an agreement or deal)

I cannot understand how the rest of the clue works.

(Other definitions for pact that I've seen before include "Treaty, formal agreement" , "Written agreement between two states" , "International treaty" , "Settlement" , "Formal agreement between parties or states" .)

I've seen this clue in The Daily Express.

Want a hint initially instead of a full solution? Install my app