Compelled former pupil to get dial fixed (9)
I believe the answer is:
obligated
'compelled' is the definition.
('obligate' can be a synonym of 'compel')
'former pupil to get dial fixed' is the wordplay.
'former pupil' becomes 'OB' (abbreviation for 'Old Boy').
'to' is a charade indicator (letters next to each other).
'fixed' indicates an anagram.
'get'+'dial'='getdial'
'getdial' anagrammed gives 'ligated'.
'ob'+'ligated'='OBLIGATED'
(Other definitions for obligated that I've seen before include "in debt" , "Bound" , "Morally compelled" .)