Fussed (7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fussed</span>' is the definition.<br/ ><span class="explanation-format__explanation">('niggle' can be a synonym of 'fuss')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for nagged that I've seen before include "Persistently harassed" , "Kept carping, criticising" , "Found fault or scolded continually" , "Criticised constantly" , "Went on" .)