Green science (7)
I believe the answer is:
ecology
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">green science</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ecology that I've seen before include "Branch of biology" , "The environment as it relates to living organisms" , "Study of creatures etc in relation to environment" , "Study of organisms and their environments" , "Bionomics" .)