Some despair at emperor being vexed (5)
I believe the answer is:
irate
'being vexed' is the definition.
(I've seen this in another clue)
'some despair at emperor' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'IRATE' is hidden in the letters of 'despair at emperor'.
(Other definitions for irate that I've seen before include "Boiling" , "Extremely angry" , "Spitting feathers" , "Magical rod" , "Annoyed, nettled" .)