The unclued lights (one of two words) display a common feature, different in each case.

Across

1 Fundamentalist group keeps imprisoning old lady (5)
6 Runs out of banners for ships (8)
14 This slow match at Ibrox, when second-rate, would lack edge (4)
15 Nosy parker holds son captive (8)
16 About a pound, one company’s cotton cloth (6)
17 Catch girl with Oscar (5)
22 Sent off, one gets close to disquiet (7)
24 Bill and Ben returned (3)
26 Dedicated Follower of Fashion — loud musical work (3)
28 Tornado scrambled, causing a stink (7)
33 County doctor...