Expel some notorious truants (4)
I believe the answer is:
oust
'expel' is the definition.
('oust' can be a synonym of 'expel')
'some notorious truants' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'OUST' can be found hidden inside 'notorious truants'.
(Other definitions for oust that I've seen before include "Remove from a position or office" , "Extract" , "Throw out" , "Expel from office or position" , "Show the door to" .)