In the lady's case, it constitutes an agreement (7)
I believe the answer is:
compact
'agreement' is the definition.
(compact can mean an agreement)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for compact that I've seen before include "'Condensed, portable (7)'" , "Dense; powder case" , "Small case for face-powder" , "Dense; formal contract" , "Dense; agreement" .)