When we talk about a drawdown profile we are referring to the time period over which an investor's pledged investment will be requested and in how many instalments.
For example, an investor pledges an investment of £300,000 in a fund which has an investment period of three years to build a portfolio of underlying investments. The drawdown profile of the fund is that the manager expects to invest a third of the total capital raised over each year of the investment period. The investors in the fund can therefore expect to have their commitment requested (or 'called') in three instalments over the investment period.
This is the opposite of how a direct investment in a private equity or private debt transaction works. In those instances, once the capital is raised and the transaction is complete, the full amount committed by investors is required by the company immediately.
If a fund starts to make distributions back to investors before the initial pledge is fully drawn, it is possible that investors will be able to fund future drawdown requests to fulfil the pledge, partially at least, from distributions that have arisen from earlier investments in the fund.