Sort of case for a diplomat (7)
I believe the answer is:
attache
I believe this is a double definition.
'sort of case' is the first definition.
'a diplomat' is the second definition.
(I've seen this before)
'for' acts as a link.
(Other definitions for attache that I've seen before include "Embassy official" , "Member of ambassador's staff" , "Junior ambassador" , "Specialist on embassy staff" , "Embassy worker" .)