1 ring
Rev Spooner's Greek letter bag and a dusty shrub (5)
When the Moon covers the Sun, you see things that are usually hidden in the glare.
The rings read clockwise, each answer beginning just after a bar. The spokes read inward from the rim. Every cell belongs to a ring answer and a spoke at once.
At six cells the two disagree. Where they do, write the spoke's letter: it sits on top, and the ring's letter is lost beneath it. Those six cells form one compact shape, so shade it in, then read the six ring letters you have covered. They name the one sight that being covered up allows.
Eleven clues carry a word that does no cryptic work at all. Solve those as though it were absent, then read the first letters of the eleven in clue order. They give the final answer (7,4), the flash that comes and goes in a second at the very edge of it.
1 ring
Rev Spooner's Greek letter bag and a dusty shrub (5)