The usage I am familiar with is
- Last night she was wearing seductive stockings.
This is because stockings very often functions the same way as pants, scissors, etc: plural in form, but referring to one object (as in nylon stockings, which gets shortened to nylons), so that we also say a pair of pants, a pair of scissors, a pair of stockings, a pair of nylons.
On the other hand, a pair of stockings do not have to be attached, so you can have two unattached stockings, just like you can have two unattached socks. In this case, I have always taken stocking to be an old-fashioned or perhaps fancier version of a sock.
It is also possible to refer to a single stocking and a single scissor--I am not sure about a single pant (except the kind of pant a dog makes, which is a different word).
As an aside, one can have a head covering called a stocking hat or stocking cap, but today this is not usually made of an actual stocking (although it can be) but fashioned so that it resembles a stocking.
Even if you wanted to use stocking in the singular, you would need to use an indefinite article:
Last night she was wearing a seductive stocking.
or, as in
Last night she was wearing a seductive stocking on her left foot/leg and a goofy stocking on her right foot/leg.