He struck some of the clergy as dictatorial (6)
I believe the answer is:
hitler
'he' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'struck some of the clergy as dictatorial' is the wordplay.
'struck' becomes 'hit' (I've seen this in another clue).
'some of' says to take the centre (I've seen 'some' mean this).
'the clergy' becomes 'prelacy' (prelacy is a kind of clergy).
'as dictatorial' becomes 'er' (I can't justify this - if you can you should believe this answer much more).
The middle of 'prelacy' is 'l'.
'hit'+'l'+'er'='HITLER'
Can you help me to learn more?
(Other definitions for hitler that I've seen before include "German dictator" , "Adolf, who made people heil" , "See 15" , "See 20" , "German Chancellor and Fuhrer, nineteen thirty three to nineteen forty five" .)