Deerclops has an attack in which it

Deerclops has an attack in which it will either swipe or pound the floor at its current target. Both animations have the same effect, damaging all mobs and structures within a radius of about 2.5 berry bushes. It usually does not immediately target the player upon arrival, having an "aggro distance" toward any mob it gets close to. Deerclops first tries to target the closest structure to the player at time of being "released" (i.e. spawned); if no structure is close enough to the player, then the player is targeted instead (although this tends to be rare). Deerclops will in general not target walls, unless the object or mob Deerclops is aiming to destroy is behind a wall. Often, walls and other structures or mobs nearby may suffer collateral damage anyway, despite what Deerclops may target. This is the reason walls don't stand up well to a Deerclops.