The unclued lights (one individually and five pairs) are of a kind.
 

Across

1    German leader put stuff back into soup (8)
5    More lascivious-sounding marketeer (6)
9    Powerless to operate, having drunk UK brown ale (10)
14    Ceilidh lacks odd members of antiquity (3)
16    Tries half the fish at 42 with starchy pudding (6, three words)
18    Brief period of enchantment (5)
20    Select group at lake bed, first (7)
22    Regular terminus — no less — for Badminton Horse Trials participant (7)
24    Because Santa left, station wagon crashed (7, two words)
25    Girl cried ‘It hurt a bit!’ (5)
26    Henry left piece of armour in ancient kingdom of West Yorkshire...