Earth science (7)
I believe the answer is:
geology
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">earth science</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that geology is a type of earth science)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for geology that I've seen before include "Science that deals with the history of rocks" , "The science of the earth's crust" , "The scientific study of the earth's crust" , "Earth science" , "Study of Earth, its rocks" .)