get your friend to hold the clutch open with his hand (that would be the spring loaded clip on the right side engine cover) while you squeeze the clutch lever. Its hard but it works. slide the wire out of the clutch lever while he has it held open with his hand.
I have a trick I use to get the clutch loose. Use an adjustable wrench to turn the arm on the clutch housing - it offers enough leverage(with one hand) to disengage the clutch to release the cable or whatever.