Sheep's hair (4)
I believe the answer is:
wool
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sheep's hair</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 wool that I've seen before include "It could become felt" , "Where the Lord Chancellor sits" , "Yarn for knitting" , "Sheep's coat" , "Pull this over the eyes to deceive" .)