How long an electron spends under the barrier during strong field tunneling ionization is still a controversial issue in attosecond science. We develop a new attoclock technique to address this problem. It exploits the carrier-envelope-phase dependence of angular streaking to extrapolate from elliptically polarized light measurements, for the first time, the deflection angles for circularly polarized light. Thus, we can avoid the ambiguity inherent to the modeling of the conventional elliptical attoclock. Our results show that the deflection angles are solely sensitive to the ionization potentials of targets and tunneling delay is a minor effect.