Working period (5)
I believe the answer is:
shift
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">working period</span>' is the definition.<br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for shift that I've seen before include "Simple dress; spell of work" , "Time when group of people are working" , "Dislodge" , "Change location" , "underskirt" .)