Strike (flint) (4)
I believe the answer is:
knap
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">strike flint</span>' is the definition.<br/ ><span class="explanation-format__explanation">(shape a flint by striking it)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for knap that I've seen before include "Break" , "Rap" , "Strike stone" , "Shape (a flint) by striking" , "Deal hammer-blow" .)