Fools told off by sensible leader (5)
I believe the answer is:
dolts
'fools' is the definition.
(I've seen this in another clue)
'told off by sensible leader' is the wordplay.
'off' is an anagram indicator.
'by' is a charade indicator (letters next to each other).
'leader' says to take the initial letters.
The first letter of 'sensible' is 's'.
'told' is an anagram of 'dolt'.
'dolt'+'s'='DOLTS'
(Other definitions for dolts that I've seen before include "Stupid fellows" , "Numbskulls" , "Idiots" , "Dullards" .)