Eight unclued lights are of a kind; the remaining two complete four words from a quote, which is appropriately positioned and must be highlighted.
 

Across

12    Old noble returning 50 eggs (4)
13    See adult in Moroni, perhaps, as this? (8)
14    Confusion restrained in mediocre way to play (9)
15    Latin on air for listener? (5)
17    Material in small type (4)
20    Hen’s firm feature (6)
21    11 Genet novel, on reading Kindle again (8, hyphened)
22    A man in active duty expressed satisfaction (5)
26    Holy church holds ball, spinning music (7)
27    Foster daughter follows fairy (4)
29    God’s aching back (4)
31    Issue from Spain has fellow worried...