Employee of an ancient emperor, briefly (4)
I believe the answer is:
temp
'employee' is the definition.
(I've seen this before)
'of an ancient emperor briefly' is the wordplay.
'of' indicates a hidden word.
'TEMP' can be found hidden inside 'ancient emperor briefly'.
(Other definitions for temp that I've seen before include "Transitory office worker" , "Non-full time employee" , "Short-time worker" , "Short-term office worker" , "N on-permanent worker" .)