Mildew (5)
I believe the answer is:
mould
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mildew</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that mildew can be written as mould)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for mould that I've seen before include "Fungal growth; template" , "Must" , "Cast; form" , "Crumbly soil" , "Cause of discoloration" .)