Study of birds (11)
I believe the answer is:
ornithology
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">study of birds</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ornithology that I've seen before include "Go, Roy Hilton (anag)" , "Study of birds" .)