  We have developed an all-particle Fock-space relativistic coupled-cluster
method to calculate the properties of two-valence atoms and ions. Using the
method we compute the properties associated with hyperfine induced $^1S_0 -
^3P^o_0$ clock transition in Al$^+$. Our result of the $^3P^o_0$ metastable
state life time, $20.20 \pm 0.91$ s, is in excellent agreement with the
experimental value, $20.60 \pm 1.4$ s [Phys. Rev. Lett. {\bf 98}, 220801
(2007)]. Our studies show that the contributions from the triple excitations,
and the corrections from the Breit interaction and QED effects are essential to
obtain accurate clock properties in Al$^+$.
