Subconvexity for symmetric square $L$-functions

Let $f$ be a holomorphic modular form of prime level $p$ and trivial nebentypus. We show that there exists a computable $\delta>0$, such that $$L\left(\tfrac{1}{2},\mathrm{Sym}^2 f\right)\ll p^{\tfrac{1}{2}-\delta},$$ with the implied constant depending only on $\delta$ and the weight of $f$.