  We construct a localized state of a scalar field in 3D spin-3 gravity. 3D
spin-3 gravity is thought to be holographically dual to W$_3$ extended CFT on a
boundary at infinity. It is known that while W$_3$ algebra is a non-linear
algebra, in the limit of large central charge $c$ a linear finite-dimensional
subalgebra generated by $W_n \, (n=0,\pm1,\pm2)$ and $L_n (n= 0,\pm1)$ is
singled out. The localized state is constructed in terms of these generators.
To write down an equation of motion for a scalar field which is satisfied by
this localized state it is necessary to introduce new variables for an internal
space $\alpha^{\pm}$, $\beta^{\pm}$, $\gamma$, in addition to ordinary
coordinates $x^{\pm}$ and $y$. The higher-dimensional space, which combines the
bulk spacetime with the `internal space', which is an analog of superspace in
supersymmetric theory, is introduced. The `physical bulk spacetime' is a 3D
hypersurface with constant $\alpha^{\pm}$, $\beta^{\pm}$ and $\gamma$ embedded
in this space. We will work in Poincar\'e coordinates of AdS space and consider
W-quasi-primary operators $\Phi_{h}(x^+)$ with a conformal weight $h$ in the
boundary and study two and three point functions of W-quasi-primary operators
transformed as $e^{ix^+L^h_{-1}} e^{\beta^+W^h_{-1}} \Phi_{h}(0)
e^{-\beta^+W^h_{-1}}e^{-ix^+L^h_{-1}}$. Here $L^h_n$ and $W^h_n$ are sl(3,R)
generators in the hyperbolic basis for Poincar\'e coordinates. It is shown that
in the $\beta^+ \rightarrow \infty$ limit, the conformal weight changes to a
new value $h'=h/2$. This may be regarded as a Renormalization Group (RG) flow.
It is argued that this RG flow will be triggered by terms $\Delta S \propto
\beta^+ W^h_{-1}+\beta^- \overline{W}^h_{-1}$ added to the action.
