Thus Government will invest in mine output after revolution (4)
I believe the answer is:
ergo
'thus' is the definition.
(I've seen this before)
'government will invest in mine output after revolution' is the wordplay.
'government' becomes 'g' (abbreviation for government).
'will invest in' indicates putting letters inside.
'mine output' becomes 'ore' (I've seen this in another clue).
'after revolution' shows that the letters should be reversed in order (letters revolve back).
'g' inserted within 'ore' is 'ogre'.
'ogre' written backwards gives 'ERGO'.
(Other definitions for ergo that I've seen before include "'Cogito, ---- sum'" , "Therefore (Latin)" , "so philosopher wrote in Latin" , "Hence" , "Consequently" .)