The cosmological constant model (ΛCDM) not only suffers from many theoretical challenges, it also presents inconsistencies between some independent observations. There exists a tension of more than 3σ between the Planck CMB measurement and the redshift space distortion (RSD) measurements in the estimation of r.m.s matter power fluctuation in the 8h−1Mpc scale, σ8. The scalar field dark energy models are potential alternate to the ΛCDM model, and resolve or at least alleviate the challenges and tension. The scalar field dark energy also cluster if the present value of the equation of state parameter deviate from - 1. In this study we consider the tachyon scalar field dark energy and analyze the effect of perturbation on the σ8 tension. We calculate the linear growth rate f for this model and compare it with ΛCDM model. We use values values of f σ8 to compare the theoretical model with RSD data. Both the models are in good agreement with data. We present constraint on σ8 − Ωm plane and show that the tension is reduced below 2σ for the perturbed scalar field dark energy model.