Dictator in regiment's HQ receiving head of state (6)
I believe the answer is:
Here is my best explanation:
'dictator in regiment's' is the definition.
'despot' can be an answer for 'dictator' (despot is a kind of dictator). I am not sure about the 'in regiment's' bit.
'hq receiving head of state' is the wordplay.
'hq' becomes 'depot' (I have seen 'Military HQ' mean 'depot' so perhaps 'hq' could also mean 'depot').
'receiving' is an insertion indicator.
'head of' says to take the initial letters.
The initial letter of 'state' is 's'.
'depot' going around 's' is 'DESPOT'.
(Other definitions for despot that I've seen before include "Cruel and oppressive ruler", "Oppressive ruler", "Tyranical dictator", "Possibly 4 [CZAR]", "Authoritarian", "nasty ruler?", "who treats others badly?", "Posted (anag)", "Oppressor" and "Dictator".)