Snitch (on)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">snitch on</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for narc that I've seen before include "Drugs agent (US)" , "Drugs officer" , "One on drugs squad" , "member of drug squad" , "Agent dealing with Charlie" .)