Mineral providing some chemicals (4)
I believe the answer is:
mica
'mineral' is the definition.
(mica is a kind of mineral)
'some chemicals' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'MICA' is hidden within 'chemicals'.
'providing' acts as a link.
(Other definitions for mica that I've seen before include "Isinglass" , "Flexible mineral found in igneous and metamorphic rocks" , "Shiny silicate mineral" , "Transparent mineral" , "Muscovite with perfect cleavage" .)