For those struggling to interpret 8D, Chambers has this for LIGHT:
"In a crossword, the word (or sometimes an individual letter in the word) on the diagram that is the answer to a clue"
The OED has:
"The item filling the spaces in a crossword puzzle as the answer to a clue".
"First light" here is simply one (I) ACROSS.
"One succeeds" is VICTOR.