The kilt or kilts.
kilts
Kilts
A tartan skirt is a kilt, which is only 4 letters, but the Irish kerns (Gaelic soldiers) wore a leine, which was really a long shirt but is often (incorrectly) depicted as a kilt.
You're thinking of the kilt
Kilt.
A tartan skirt is a kilt (four letters) or kilts (plural).
a kilt.
The Scottish tartan 'skirt' - is called a kilt.
A word for a tartan skirt is plaid.
A skirt which is tartan in colour.
One can purchase a tartan skirt in stores that specialise in Scottish ladieswear, though there are numerous of other fashion stores that carry either tartan or plaid skirt.
A tartan skirt is a "kilt." Perhaps the clue was plural.