Split city in Cambridgeshire? Hardly! (8)
I believe the answer is:
severely
'hardly' is the definition.
(thesaurus)
'split city in cambridgeshire?' is the wordplay.
'split' becomes 'sever' (sever can mean to split or separate).
'city in cambridgeshire?' becomes 'ely' (I've seen this before).
'sever'+'ely'='SEVERELY'
(Other definitions for severely that I've seen before include "With sternness" , "In rigorous, exacting manner" , "very badly" , "In a stern manner" , "Sternly or gravely" .)