One unclued light (four words) is the title of a 40 recorded by 43 (two words). This title forms a cryptic indication of one unclued light, which defines each of the other unclued lights.
 

Across

11    Unlucky guys taken in by bad old lie (9, hyphened)
12    Try to turn round cubic mineral (4)
17    Noted folio poorly made (5)
20    Proceed, worried after revolutionary call (7)
21    Favouring relations, quickly write back (7)
24    Tea in family’s village in Scotland (7)
25    Journal from Suez in Egypt (5, hyphened)
26    Old letter with very large moral significance (5)
28    Mass...