Relating to digestion (6)
I believe the answer is:
peptic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">relating to digestion</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for peptic that I've seen before include "Kind of ulcer in stomech or duodenum" , "of the digestive system" , "may be aiding digestion" , "Relating to digestion - kind of ulcer" , "Of digestion, and a related ulcer" .)