Thus in power, government (4)
I believe the answer is:
ergo
'thus' is the definition.
(I've seen this in another clue)
'in power government' is the wordplay.
'in' says the answer is hidden in the clue.
'ERGO' can be found hidden inside 'power government'.
(Other definitions for ergo that I've seen before include "Consequently" , "as a consequence" , "for this reason" , "'Therefore, to the old Romans (4)'" , "'Cogito, ---- sum'" .)