Subject characters in college ill-advisedly took up (5)
I believe the answer is:
liege
'subject' is the definition.
(I've seen this before)
'characters in college ill-advisedly took up' is the wordplay.
'characters in' indicates the answer is hidden within the clue.
'took up' shows that the letters should be reversed in order (I've seen 'taken up' mean this).
'egeil' is hidden within 'college ill advisedly'.
'egeil' reversed gives 'LIEGE'.
(Other definitions for liege that I've seen before include "Subject in history" , "Old sovereign" , "Feudal lord or Belgian city" , "Vassal; city in Belgium" , "A person holding land under feudalism" .)