Let \(\phi \) be a fixed Hecke–Maass form for \(\textrm{SL}_3 ({\mathbb {Z}})\) and \(u_j \) traverse an orthonormal basis of Hecke–Maass forms for \(\textrm{SL}_2 ({{\mathbb {Z}}}) \) . Let \(1/4+t_j^2\) be the Laplace eigenvalue of \(u_j \) . In this paper, we prove the mean Lindelöf hypothesis for the second moment of \( L (1/2+it_j, \phi \times u_j) \) on \( T < t_j \leqslant T + \sqrt{T} \) . Previously, this was proven by Young on \( t_j \leqslant T\) . Our approach is more direct as we do not apply the Poisson summation formula to detect the ‘Eisenstein–Kloosterman’ cancellation.