Mineral corporation securing aluminium contract initially (6)
I believe the answer is:
talcum
'mineral' is the definition.
(talcum is a kind of mineral)
'corporation securing aluminium contract initially' is the wordplay.
'corporation' becomes 'tum' (I've seen this before).
'securing' means one lot of letters goes inside another.
'aluminium' becomes 'al' ('Al' can be a synonym of 'aluminium').
'initially' suggests taking the first letters.
The first letter of 'contract' is 'c'.
'al'+'c'='alc'
'tum' placed around 'alc' is 'TALCUM'.
(Other definitions for talcum that I've seen before include "Standard body powder" , "Kind of powder" , "Scented toilet powder" , "Bathroom mineral" , "Dusting powder" .)