The mood of The Last Emperor (6)
I believe the answer is:
temper
'the mood' is the definition.
(temper is one's mood or state of mind)
'of the last emperor' is the wordplay.
'of' indicates the answer is hidden within the clue.
'TEMPER' is hidden within 'last emperor'.
(Other definitions for temper that I've seen before include "(Calm or furious) disposition" , "Harden metal by heating and cooling" , "Rage" , "Bad humour" , "Moderate; ill humour" .)