Neither M nor F (6)
I believe the answer is:
neuter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">neither m nor f</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 neuter that I've seen before include "Neither m nor f" , "Neither masculine nor feminine gender" , "Tureen (anag.)" , "Make ineffective; gender" , "Of noun, neither masculine nor feminine" .)