Penicillin, eg (10)
I believe the answer is:
antibiotic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">penicillin eg</span>' is the definition.<br/ ><span class="explanation-format__explanation">(penicillin is a kind of antibiotic)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for antibiotic that I've seen before include "Infection treatment" , "Medicine destroying micro-organisms" , "Substance that destroys bacteria" , "Medication" , "Remedy" .)