(i) In chlorobenzene, due to resonance, there is a partial double bond character, so bond length is short.
(ii) The dipole moment of chlorobenzene is lower as bond length is shorter $\left(\mathit{\mu }=\mathit{q}\times \mathit{d}\right)$ due to resonance and $\mathit{s}{\mathit{p}}^2$ hybridized carbon, it has less tendency to release electrons than the $\mathit{s}{\mathit{p}}^3$ hybrid of $\mathrm{C}-\mathrm{Cl}$ (in cyclohexyl chloride). Hence, chlorobenzene is more electronegative resulting in decrease in polarity of $\mathrm{C}-\mathrm{Cl}$ bond.