Mineral found in hospital cabinets (4)
I believe the answer is:
talc
'mineral' is the definition.
(talc is a kind of mineral)
'in hospital cabinets' is the wordplay.
'in' says the answer is hidden in the clue.
'TALC' can be found hidden inside 'hospital cabinets'.
'found' is the link.
(Other definitions for talc that I've seen before include "Softest mineral on Mohs hardness scale" , "Baby powder" , "After-bath powder" , "In brief, popular body powder" , "(Mineral providing) powder" .)