Uncertainty principle physicist (10)
I believe the answer is:
heisenberg
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">uncertainty principle physicist</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 heisenberg that I've seen before include "Nobel prize-winner" , "Exact location and speed ever unknown, I suggested" , "'Uncertainty principle' mathematical physicist, d. 1976 -- begins here (anag)" , "Man of principle" , "to give name in uncertainty" .)