Part of speech; verb modifier (6)
I believe the answer is:
adverb
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">part of speech</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(adverb is a kind of part of speech)</span><br/ ><br/ >'<span class="explanation-format__original">verb modifier</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for adverb that I've seen before include "Term of modification" , "Action word qualifier" , ""Quickly" is one, for example" , "Modifying word (gram.)" , "Braved (anag)" .)