Gradual wearing away (7)
I believe the answer is:
erosion
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gradual wearing away</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for erosion that I've seen before include "Disintegration" , "dying away" , "Deterioration of soil etc" , "Mechanical process of wearing something down" , "Action of wearing away" .)