What does the cryptic crossword clue "Illumination needed for blatant hold-up? (8)" mean?

The definition is "Illumination needed for blatant hold-up?". The wordplay uses a cryptic definition. Cryptic definition The answer is DAYLIGHT.

Illumination needed for blatant hold-up? (8)

Guardian Cryptic #29119 | 20 Across | 2023-07-11 flower