Working with axes to produce mineral (4)
I believe the answer is:
onyx
'mineral' is the definition.
(onyx is a kind of mineral)
'working with axes' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'with' is a charade indicator (letters next to each other).
'axes' becomes 'yx' (Y axis and X axis).
'on'+'yx'='ONYX'
'to produce' is the link.
(Other definitions for onyx that I've seen before include "Cameo material" , "Variety of agate used for making cameos" , "Hard stone with coloured layers" , "Form of quartz" , "Agate with different layers of colour" .)