Manipulate fraudulently (3)
I believe the answer is:
'manipulate fraudulently' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rig that I've seen before include "Oil-drilling device" , "Oil platform" , "Masts, spars and sails on a vessel" , "Apparatus; (boat's) sails" , "Outfit; fix" .)