Sinister business that's apparent throughout the universe (4,6)
I believe the answer is:
dark matter
'that's apparent throughout the universe' is the definition.
(the universe is full of dark matter)
'sinister business' is the wordplay.
'sinister' becomes 'dark' (I've seen this in another clue).
'business' becomes 'matter' (business can mean some matter or situation).
'dark'+'matter'='DARK MATTER'
(Other definitions for dark matter that I've seen before include "A large proportion of the mass of the universe" , "In astronomy, theoretical non-luminous material" .)