Sir,
you have not mentioned what is the nature of cleaning required. is your farm is cultivated, is your farm left uncultivated for many years.
these are ways for cleaning .
1.manual cleaning: generally done by group people some contractors available who will based on damage they will charge.
2.tracter cleaning:- you can hire tractor on rent basis with special equipments attached will clean your land.
3.JCB cleaning:- If your land is left uncultiated for long periods you can go far such cleaning.
4.Chemical :- if the weed damage is minimum you can spray weedicide Glyphosite a systemic insecticide.