Idiot told off (4)
I believe the answer is:
dolt
'idiot' is the definition.
(I know that idiot can be written as dolt)
'told off' is the wordplay.
'off' indicates anagramming the letters.
'told' anagrammed gives 'DOLT'.
(Other definitions for dolt that I've seen before include "Dull or stupid fellow" , "Dunce" , "Stupid person" , "dope" , "Dullard" .)