Mutual agreement subject to status? (13)
I believe the answer is:
understanding
'mutual agreement' is the definition.
'subject to status?' is the wordplay.
'subject to' becomes 'under' (I've seen this before).
'status?' becomes 'standing' (standing is a kind of status**).
'under'+'standing'='UNDERSTANDING'
(Other definitions for understanding that I've seen before include "Compassion" , "Getting" , "Knowledge" , "Knowing" , "compassionate" .)