Gosh - fairy started nearest to the earth (7)
I believe the answer is:
perigee
'nearest to the earth' is the definition.
I can't tell whether this definition defines the answer.
'gosh fairy started' is the wordplay.
'gosh' becomes 'gee' (I've seen this in another clue).
'fairy' becomes 'peri' (Persian mythological being).
'started' is a charade indicator (letters next to each other).
'gee' put after 'peri' is 'PERIGEE'.
Can you help me to learn more?
(Other definitions for perigee that I've seen before include "Point of orbit nearest earth" , "Lowest orbit point" , "A low point" , "Point of closest approach" , "Point of orbit closest to the earth" .)