Apply oil or grease (9)
I believe the answer is:
lubricate
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">apply oil</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">grease</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for lubricate that I've seen before include "Apply oil/grease" , "Oil (a mechanism)" , "Apply oil or grease to" , "Make slippery" , "Coat with oil to reduce friction" .)