Plant providing semiconducting material — mass turned out (8)
I believe the answer is:
geranium
'plant' is the definition.
(geranium is a plant)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for geranium that I've seen before include "Cultivated flower often seen in window box" , "Pelargonium (loosely)" , "Cranesbill plant" , "Flower confused with pelargonium" , "Showy garden flower, often seen in window-boxes" .)