Strong string (5)

I believe the answer is:
twine
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">strong string</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 twine that I've seen before include "twist" , "Thin cord" , "Strong thread or string" , "Tough string" , "Twisted cord" .)