Mineral regularly cheaper -- it is in China (9)
I believe the answer is:
haematite
'mineral' is the definition.
(haematite is a kind of mineral)
'regularly cheaper it is in china' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'is in' is an insertion indicator.
'china' becomes 'mate' ('China plate' is rhyming slang for 'mate').
The alternating letters of 'cheaper' are 'hae'.
'it' put into 'mate' is 'matite'.
'hae'+'matite'='HAEMATITE'
(Other definitions for haematite that I've seen before include "source of iron" , "Iron ore" .)