Half a fortnight (4)
I believe the answer is:
week
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">half a fortnight</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for week that I've seen before include "Calendar period" , "Part of the year" , "Seven day period" , "A long time in politics?" , "Period of time; sounds like feeble" .)