Queen about to consume line in powder? (4)
I believe the answer is:
talc
'powder?' is the definition.
(talcing is a kind of powdering)
'queen about to consume line' is the wordplay.
'queen' becomes 'cat' (a queen is a female cat**).
'about' is a reversal indicator.
'to consume' means one lot of letters goes inside another.
'line' becomes 'l'.
'cat' in reverse letter order is 'tac'.
'tac' placed around 'l' is 'TALC'.
'in' is the link.
(Other definitions for talc that I've seen before include "Powdered mineral" , "Soft white powder" , "Bathroom dusting powder" , "After-bath powder" , "Bathroom powder (abbr)" .)