The unclued lights (two of two words) are of a kind.

Across

12 To make sense of Sun puzzle, many go on and on (10)
14 17 regularly discloses gun? (3)
15 One fated, cruelly, to have no ear? (8, hyphened)
17 A medic’s morning tipple? (5, two words)
19 We’re told Roman king suffers ruin (6)
22 Rallying cry evoking terrible noises (6)
24 One in a suit amongst the artillery (5)
26 One nominated for a benefice is here mid-week (9)
27 Chemical compounds – a kilo lad’s carried away (9)
29 Novelist whom Douglas Kidman embraces (5)
31 Eloquent and well-off, without a female in the lead (6)
34 Bouts...