In short, the governmental head named Barnaby (5)
I believe the answer is:
rudge
'named barnaby' is the definition.
'rudge' can be an answer for 'barnaby' (Barnaby Rudge is a Dickens novel). I am not sure about the 'named' bit.
'in short the governmental head' is the wordplay.
'in' indicates putting letters inside.
'short the' becomes 'rude' (I can't justify this - if you can you should give a lot more credence to this answer).
'head' suggests taking the first letters.
The first letter of 'governmental' is 'g'.
'rude' going around 'g' is 'RUDGE'.
Can you help me to learn more?
(Other definitions for rudge that I've seen before include "Dickensian halfwit" , "Dickensian character" , "'Barnaby - - ' by Charles Dickens" , "Dickens novel 'Barnaby .....'" , "Dickens character" .)