2Dropped by
a Skeletron summon in your pocket
Equip it and the Clothier becomes killable by anything, including you, stray falling stars and other NPCs. Kill him after dark and Skeletron rises out of him on the spot. That is far more convenient than the usual route, since you do not have to travel to the dungeon and talk to anyone to start the fight.
it survives the summon
The Guide's doll gets destroyed in the process. This one does not, and lava will not eat it either, so a single drop covers every Skeletron attempt you will ever make. It cannot be reforged, so there are no modifiers to chase and no reason to keep a spare.
the small money loop
The Clothier drops his hat when he dies and Skeletron pays out on top of that, which is a tidy little routine. The ceiling is one run per night, since he will not move back in until morning, so it is pocket money rather than a farm worth building around.