MTF stands for Margin Trading Facility (commonly referred to as Margin Funding) wherein when you have to trade / invest, you bring in part of the funds of the trade (known as your margin) and the stock broker (in this case Dhan) brings in the remaining funds on behalf of you - so that you can buy the desired shares with lower margins / capital required from your end.
Note: The exchange always requires the full capital, so Dhan arranges for the same in this case for a smaller interest amount.

To know more click here : Margin Trading Facility