Main point of government — it's complex (4)
I believe the answer is:
gist
'main point' is the definition.
(the main point or meaning of something)
'government it's complex' is the wordplay.
'government' becomes 'g' (abbreviation for government).
'complex' indicates anagramming the letters.
'its' with letters rearranged gives 'ist'.
'g'+'ist'='GIST'
'of' is the link.
(Other definitions for gist that I've seen before include "Main idea, kernel of matter" , "Main point of the matter" , "Drift" , "Central idea" , "Essential point or general sense of anything" .)