Extreme dictators having dropped to ground (7)
I believe the answer is:
drastic
'extreme' is the definition.
(I've seen this in another clue)
'dictators having dropped to ground' is the wordplay.
'having dropped' indicates named letters should be taken away.
'ground' indicates anagramming the letters ('grind' the letters into a new form).
'dictators' with 'to' taken away is 'dictars'.
'dictars' is an anagram of 'DRASTIC'.
(Other definitions for drastic that I've seen before include "Harsh, severe" , "Uncompromising" , "Extreme - violent" , "Severe and far-reaching" , "Extreme - forceful" .)