Strike (flint) (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
knap
'strike flint' is the definition.
(shape a flint by striking it)
This is the entire clue.
(Other definitions for knap that I've seen before include "Break" , "Rap" , "Strike stone" , "Shape (a flint) by striking" , "Deal hammer-blow" .)