Mr Clegg received a rough ride from the 5 live listeners, many of whom were his constituents, who accused him of going back on his word over student tuition fees.
"Jimmy was shining the ball and when he turned it over it was almost as if he was absent-mindedly assessing the rough side, " he told BBC Radio 5 live.
Britain's Pensions Commission has used a net replacement rate of 80% for workers on average incomes as a rough guide to whether they will have enough to live on in retirement.
He said that by offering "individually tailored support" the charity can help rough sleepers to get back on their feet and ultimately to live independent lives.