Irritant for a princess (3)
I believe the answer is:
pea
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">irritant for a princess</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for pea that I've seen before include "Cause of a princess's insomnia?" , "It grows in 23 Down" , "Tiny stone" , "12 in a pod" , "Spherical vegetable" .)