current flows from positive side of battery. When it flows down from P to Q the current has two components...one directly down ( which we will ignore) and a component pointing to the left of the page. Consider this component to be the current used in the motor effect. Using right hand push rule...current is to left....field is ( almost vertically) down ( from N to s) and therefore force is towards you or out of page. Since this is a completely symmetric situation the force is always towards the viewer and therefore the coil PQ turns clockwise.
Note 1: field is down the glass ( of mercury) as the external field points in a sort of convexy way but can be considered to be ( sort of) uniform directed downwards.