Island administered under Sark that’s out of bounds? (5)
I believe the answer is:
arran
'island' is the definition.
(Isle of Arran in Scotland)
'administered under sark that's out of bounds?' is the wordplay.
'administered' becomes 'ran' (run can mean to administer or control).
'under' is a charade indicator (letters next to each other).
'that's out of bounds?' says to take the centre (I've seen 'out of bounds' mean this (the bounds or edges of the word are removed)).
The middle of 'sark' is 'ar'.
'ran' put after 'ar' is 'ARRAN'.
(Other definitions for arran that I've seen before include "Isle near Firth of Clyde" , "Scottish island" , "Firth of Clyde island" , "Scottish territory" .)