Nuclear piles found when the moon is within the earth’s shadow (5,7)
I believe the answer is:
lunar eclipse
'shadow' is the definition.
(I know that lunar eclipse is a type of eclipse)
'nuclear piles found when the moon is within the earth's' is the wordplay.
'nuclear piles' can be anagrammed to 'LUNAR ECLIPSE'.
Though, I am not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for lunar eclipse that I've seen before include "Heavenly event" , "Satellite in thirty five" , "Phenomenon when sunlight can't reach our satellite" , "astronomical phenomenon" , "During which the earth's shadow may be seen" .)