Our Founding Fathers were very careful to separate executive and legislative powers, very much different and in reaction to the Westminster parliamentary system they had after all rebelled against. So I don't see the Congress having the power to go beyond jailing someone to force them to testify (their being the nation's Grand Inquisitor is part of our small 'c' constitution if not explicitly in the written one).

If you want to see Clapper clapped in irons, elect a non-Democratic Party President with a spine, and hope he doesn't get a pardon before then.