Possible Clues:

• Garment sold at a concert
• Exercise apparel
• Bit of wearable merch
• What a cannon might shoot in an NBA arena
• Souvenir choice
• Where you might see the message formed by the last words in 21-, 32-, 42- and 54-Across
• Straight out without a good top!
• Logo displayer, maybe
• Clothing soaked at the front in XXX, having shrunk
• Jeans go-with