If a force F applies on a body and it allows it to move an infinitely small distance d, then work done is given by dW=F.ds and for a path, integrate it putting lower limits (starting position) and upper limits (ending position).

Here, in the given question,

since a complete rotation is made i.e. net displacement is zero. i.e.

i.e. The work done by the electric field on the rotating charge in one complete revolution is zero.