For example, If you hold 1 share which is worth Rs. 1000 in the market right now and you choose to pledge it to get some extra margin to be utilized in trading, you can do so on Groww. Let's say that Groww has a haircut of 30% on this stock, once your pledge request is executed, you will recieve Rs. 1000 - (30% X 1000) i.e. Rs. 700 in your Groww balance as Pledge margin.
Please note that haircut is just a protective measure, it's not a charge, the value of your stock is still Rs. 1000 in the market and you'll get back your holdings once you unpledge your holdings. You can then choose to sell this holding at the market value.