Growth under the skin (4)
I believe the answer is:
cyst
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">growth under the skin</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for cyst that I've seen before include "Benign growth" , "Bladder" , "Abnormal closed sac in a body" , "Sac in the body containing liquid secretion" , "Small sac in body (that may form abnormal lump)" .)