Linen source (4)
I believe the answer is:
flax
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">linen source</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for flax that I've seen before include "Linen thread" , "Blue flowering plant cultivated for its seeds and fibre" , "leaves from it make cloth" , "Fibre woven to make linen" , "Fibre from a plant with blue flowers, used to make linen" .)