2 describes a pair of unclued lights (three words altogether), which in turn include the others.
 

Across

12    Single by pop group: ‘Go for violent crime’ (8)
13    Beast’s sardonic-sounding refusal (5)
14    Wing and tail feathers missing one month (8)
16    Book I inscribed for myself? (4)
20    Will’s to resurrect a year’s work (6)
21    Dealer’s only rule: concealing clubs (6)
22    A positive plan backfires, that’s plain (5)
24    Not long before one pleasure of paradise? (5)
26    Most merciful end, laid out in coffin (7)
27    Manages to secure suitable instruction for Christian society (7)
28    Security organisation seizes Catholic roughly (5)
32    Maintain unity, staying constant (5)
34    Nelson,...