Fender in this context means:

the pressed and formed sheet-metal part mounted over the road wheels of an automobile, bicycle, etc., to reduce the splashing of mud, water, and the like.


a device on the front of a locomotive, streetcar, or the like, for clearing the track of obstructions.

In view of your explanation, I think the second meaning is more appropriate. It appears that there is no exact Hindi synonym for this technical term. We may use one of the two options suggested above.