God's personal assistant getting very upset (6)
I believe the answer is:
osiris
'god's' is the definition.
(Egyptian god)
'personal assistant getting very upset' is the wordplay.
'personal assistant' becomes 'iris' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'getting' is a charade indicator (letters next to each other).
'very' becomes 'so' (both can mean 'extremely').
'upset' says the letters should be written backwards.
'so' reversed gives 'os'.
'iris' put after 'os' is 'OSIRIS'.
Can you help me to learn more?
(Other definitions for osiris that I've seen before include "Egyptian god of the dead" , "once highly esteemed by Egyptians" , "Egyptian deity" , "underworld boss" , "one held to be divine" .)