  We use 3D hydrodynamical models to investigate the effects of massive star
feedback from winds and supernovae on inhomogeneous molecular material left
over from the formation of a massive stellar cluster. We simulate the
interaction of the mechanical energy input from a cluster with 3 O-stars into a
giant molecular cloud (GMC) clump containing 3240 solar masses of molecular
material within a 4 pc radius. The cluster wind blows out of the molecular
clump along low-density channels, into which denser clump material is
entrained. We find that the densest molecular regions are surprisingly
resistant to ablation by the cluster wind, in part due to shielding by other
dense regions closer to the cluster. Nonetheless, molecular material is
gradually removed by the cluster wind during which mass-loading factors in
excess of several 100 are obtained. Because the clump is very porous, 60-75 per
cent of the injected wind energy escapes the simulation domain, with the
difference being radiated. After 4.4 Myr, the massive stars in our simulation
begin to explode as supernovae. The highly structured environment into which
the SN energy is released allows even weaker coupling to the remaining dense
material and practically all of the SN energy reaches the wider environment.
The molecular material is almost completely dispersed and destroyed after 6
Myr. The escape fraction of ionizing radiation is estimated to be about 50 per
cent during the first 4 Myr of the cluster's life. A similar model with a
larger and more massive GMC clump reveals the same general picture, though more
time is needed for it to be destroyed.
