Kent lose terribly important opening all-rounder? (8,3)
I believe the answer is:
skeleton key
'opening all-rounder?' is the definition.
(skeleton key opens all locks in a particular site)
'kent lose terribly important' is the wordplay.
'terribly' indicates an anagram.
'important' becomes 'key' (similar in meaning).
'kent'+'lose'='kentlose'
'kentlose' with letters rearranged gives 'skeleton'.
'skeleton'+'key'='SKELETON KEY'
(Other definitions for skeleton key that I've seen before include "Device that can open different locks" , "it opens many doors" , "Versatile opener" , "Opener of many locks" , "Master admitting" .)