The unclued lights, (two of two words), are of a kind. Chambers does not give the solution at 12 Across. So as to avoid alternative thematic solutions at 28A, solvers should know that the first letter is the same as the final one.
 
 Across
2    Amblers won’t be adapting military item (13, three words)
12    Reported as irresponsible piano disposal (6, two words)
14    Cure for one at sea (4)
15    Yearn to get control of free shot in hockey (10, two words)
16    Tenements holding ordinary footlights (6)
18    Sayings of one involved in gaol-break (5)
19    Type setter and mason’s assistant? (9)
22    Abner’s boss that is...