Field in which one studies the earth (9)
I believe the answer is:
geography
This clue might be a double definition.
'field in which one studies' is the first definition.
'geography' can be an answer for 'field' (geography is a kind of field). I'm unsure of the rest of the definition.
'the earth' is the second definition.
(thesaurus)
Can you help me to learn more?
(Other definitions for geography that I've seen before include "Study of earth's topography and man's responses to it" , "The study of the earth" , "Scientific study of earth's surface" , "15 down subject" , "school subject" .)