The same 26 appears six times in 1D. Remaining unclued lights exemplify its different meanings. The 26 will appear diagonally in the completed grid and must be shaded.
 

Across

7    Chief cycling daily (4)
11    Young man has time for special author (5)
12    Food Victor feeds forces (6)
13    A road alongside hill in Cheshire? (7)
15    Heart of some lady fair (4)
17    Maybe Oxford lecturer has eyepiece with unique cavity (10)
18    Water casks? Take in large cups (8)
21    Birds from region around Germany (5)
22    Friend hoards money in an unfriendly way (7)
23    Rory downsized huge cargo boats (5, hyphened)
29    Sheep in wood heard (3)
33   ...