Fasten again (5)
I believe the answer is:
retie
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fasten again</span>' is the definition.<br/ ><span class="explanation-format__explanation">('tie' is an answer for 'fasten' so perhaps 'retie' is OK for 'fasten again')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for retie that I've seen before include "Link up again" , "restore connection" , "Make knot or bow again" , "make another knot" , "Bind again" .)