Rum delivery in case (7)
I believe the answer is:
oddball
'case' is the definition.
(I've seen this before)
'rum delivery' is the wordplay.
'rum' becomes 'odd' (rum can mean strange or dubious).
'delivery' becomes 'ball' (ball is a kind of delivery).
'odd'+'ball'='ODDBALL'
'in' is the link.
(Other definitions for oddball that I've seen before include "Weird" , "Weirdo" , "Eccentric person like uneven sphere" , "Bold lad may be eccentric" , "Unusual" .)