Revolutionary princess rises up behind (2,7)
I believe the answer is:
in arrears
'behind' is the definition.
(thesaurus)
'revolutionary princess rises up' is the wordplay.
'revolutionary' shows that the letters should be reversed in order.
'princess' becomes 'rani' (I've seen this before).
'rises up' becomes 'rears' ('rear' can be a synonym of 'rise up').
'rani' back-to-front is 'inar'.
'inar'+'rears'='IN ARREARS'
(Other definitions for in arrears that I've seen before include "Owing" , "Behind with payments" , "Overdue" , "Behindhand (with rent)" , "Late with payments" .)