Government's in control, as a rule (5)
I believe the answer is:
reign
'as a rule' is the definition.
(I've seen this before)
'government's in control' is the wordplay.
'government' becomes 'g'.
'in' means one lot of letters goes inside another.
'control' becomes 'rein' (rein is a kind of control**).
'g' put within 'rein' is 'REIGN'.
(Other definitions for reign that I've seen before include "Rule - dominate" , "Niger (anag)" , "are unbeatable!" , "Occupy the throne" , "Govern" .)