JKR's description of a 'Portkey' on the Pottermore website would suggest that portkeys can only be made from objects, not living things:
Almost any inanimate object can be turned into a Portkey. Once
bewitched, the object will transport anyone who grasps it to a
pre-arranged destination. A Portkey may also be enchanted to transport
the grasper (or graspers) only at a given time. In this way, the
arrivals and departures of great numbers of witches and wizards can be
staggered, enabling such events such as the Quidditch World Cup to
take place with few security breaches. Pottermore Wiki
The same quote also indicates that it must be "grasped". Enchanting a set of clothes in-situ would probably be quite effective (unless you can think of a way of getting them off without grasping them) although as a piece of offensive magic it would be relatively useless since the spell seems to require several seconds to take effect, long enough to remove the offending article.
"For a moment the kettle trembled, glowing with an odd blue light; then
it quivered to rest, as solidly black as ever."