One ‘unclued’ light, as the title suggests, can be paired (on one occasion twice) with each of the other unclued lights, (one of two words), all verifiable in Brewer. Alphabetical order takes priority in the unclued solution at 36A.
 

Across

 
1    Builders’ aid marketed outside greasy spoon in Gabon (11)
7    Chap who’s affected flashy older people, primarily (3)
13    Parts of heart sometimes rum and Asti pepped up (7)
15    Barlow’s holding Deirdre, finally laments (5)
16    Thinks the duck had returned (5)
17    Sale is arranged for French bundle (6)
18    Angry marauder topped (5)
21    Bird circling round a fenced enclosure (5)
22    Old advice about dry...