Inoculate (8)
I believe the answer is:
immunise
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">inoculate</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for immunise that I've seen before include "Make safe from infection" , "Make resistant to disease" , "Make resistant to infection as by innoculation" , "Vaccinate" , "Inoculate against" .)