Environmental science (7)
I believe the answer is:
ecology
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">environmental science</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ecology that I've seen before include "Study of relations between organisms and their environment" , "Green science" , "Scientific study of living things in their environment" , "Study of organisms in relation to their environment" , "Green study or movement" .)