Continental's day in a prison (7)
I believe the answer is:
african
'continental's' is the definition.
(I've seen this before)
'day in a prison' is the wordplay.
'day' becomes 'fri'.
'in' means one lot of letters goes inside another.
'prison' becomes 'can' (the can is American slang for prison).
'a'+'can'='acan'
'fri' going within 'acan' is 'AFRICAN'.
(Other definitions for african that I've seen before include "Kikuyu possibly" , "Continental" , "One from south of the Mediterranean" , "- Violet; - elephant" , "For example, Algerian" .)