Grumpy person (6)
I believe the answer is:
grouch
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">grumpy person</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 grouch that I've seen before include "one known for grumbling" , "Grumble - complain" , "Person continually grumbling" , "Grumbler - gripe" , "Complain(ing person)" .)