For a monoid M and a subsemigroup S of the full transformation semigroup T n , the wreath product M ≀ S is defined to be the semidirect product M n ⋊ S, with the coordinatewise action of S on M n . The full wreath product M ≀ T n is isomorphic to the endomorphism monoid of the free M -act on n generators. Here, we are particularly interested in the case that S = Sing n is the singular part of T n , consisting of all non-invertible transformations. Our main results are presentations for M ≀Sing n in terms of certain natural generating sets, and we prove these via general results on semidirect products and wreath products. We re-prove a classical result of Bulman-Fleming that M ≀ Sing n is idempotent-generated if and only if the set M/L of L -classes of M forms a chain under the usual ordering of L -classes, and we give a presentation for M ≀ Sing n in terms of idempotent generators for such a monoid M . Among other results, we also give estimates for the minimal size of a generating set for M ≀ Sing n , as well as exact values in some cases (including the case that M is finite and M/L is a chain, in which case we also calculate the minimal size of an idempotent generating set). As an application of our results, we obtain a presentation (with idempotent generators) for the idempotent-generated subsemigroup of the endomorphism monoid of a uniform partition of a finite set.