Ordinary student interrupts important American right-winger as required (10)
I believe the answer is:
obligatory
'required' is the definition.
(similar in meaning)
'ordinary student interrupts important american right-winger' is the wordplay.
'ordinary' becomes 'O' (abbreviation e.g. O-Levels).
'student' becomes 'l' (as in L-plates for learner drivers).
'interrupts' is an insertion indicator.
'important american' becomes 'biga' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'right-winger' becomes 'Tory' (Tory is an example).
'l' going inside 'biga' is 'bliga'.
'o'+'bliga'+'tory'='OBLIGATORY'
'as' acts as a link.
Can you help me to learn more?
(Another definition for obligatory that I've seen is " Binding".)