  For an ample Hausdorff groupoid $G$, and the Steinberg algebra $A_R(G)$ with
coefficients in the commutative ring $R$ with unit, we describe the centraliser
of subalgebra $A_R(U)$ with $U$ an open closed invariant subset of unit space
of $G$. In particular, we obtain that the algebra of the interior of the
isotropy is indeed the centraliser of the diagonal subalgebra of Steinberg
algebra. This will unify several results in the literature and the
corresponding results for Leavitt path algebras follow.
