If, in straight and level unaccelerated flight, the aileron is displaced and none of the other controls is moved, the aircraft will roll with the result that the lift vector will be displaced from the vertical causing sideslip. The directional stability of the aircraft will cause yaw and, if uncorrected, the aircraft will enter a spiral descent.
Roll => Sideslip => Yaw. What else is there to explain?
Oh dear, having already incurred the wrath of the invigilator, this is probably unwise.
However!
Judging from many of the contributions on this thread, what else seems to need explaining is the mechanism for 'correcting the yaw to prevent a spiral descent' (if indeed that is what one does
)
Islander2......11+ (marginal pass)