Exclude a bachelor at the detention centre (3)
I believe the answer is:
ban
'exclude' is the definition.
(I've seen this in other clues)
'a bachelor at the detention centre' is the wordplay.
'a bachelor' becomes 'ba' (the qualification: Bachelor of Arts).
'at' is a charade indicator (letters next to each other).
'centre' says to take the centre.
The centre of 'detention' is 'n'.
'ba'+'n'='BAN'
(Other definitions for ban that I've seen before include "outlaw" , "'Forbid, prohibit (3)'" , "Officially prohibit" , "Exile" , "Censor or proscribe" .)