A right pair's accepting University's tough (7)
I believe the answer is:
arduous
'tough' is the definition.
(thesaurus)
'a right pair's accepting university's' is the wordplay.
'a right' becomes 'ar' (I've seen this in other clues**).
'pair's' becomes 'duos' (duo is a kind of pair).
'accepting' means one lot of letters goes inside another.
'university' becomes 'u'.
'duos' going around 'u' is 'duous'.
'ar'+'duous'='ARDUOUS'
(Other definitions for arduous that I've seen before include "Demanding great effort" , "Backbreaking" , "Requiring hard work" , "Burdensome" , "Toilsome" .)