Hey Swapna.

According to the ONGC Recruitment from CLAT, the eligibility criteria laid out is that you need to have a 3 year or 5 year integrated law degree from a recognised institute by the Bar council of India. You need to score a minimum aggregate of atleast 60% in your LLB degree to be eligible for ONGC Recruitment through CLAT. As your aggregate is 56% you don't seem to be eligible for this.

Best of luck