Corroding (7)
(Other definitions for rotting that I've seen before include "Going bad" , "corruption?" , "Putrid" , "Decaying" , "Sultanate in NW Borneo" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">corroding</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that rusting is a type of corroding)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Another definition for rusting that I've seen is " Corroding".)