A part of speech (6)
I believe the answer is:
adverb
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a part of speech</span>' is the definition.<br/ ><span class="explanation-format__explanation">(adverb is a kind of part of speech)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for adverb that I've seen before include "for example, determinedly" , "Verb qualifier" , "Modifying word (gram.)" , "Word modifying another" , "Word that qualifies an action" .)