Dorothy cuddling a pupil, the fool! (4)
I believe the answer is:
dolt
'the fool' is the definition.
(I've seen this before)
'dorothy cuddling a pupil' is the wordplay.
'dorothy' becomes 'dot' (short for Dorothy).
'cuddling' indicates putting letters inside (inserted letters are embraced or welcomed in).
'a pupil' becomes 'L' (as in a learner driver with L-plates on their car).
'dot' enclosing 'l' is 'DOLT'.
(Other definitions for dolt that I've seen before include "Idiot" , "Dull or stupid fellow" , "Stupid person" , "Slow-witted type" , "Dimwit" .)