This person's about to enter a shade abrasive (6)
I believe the answer is:
pumice
'abrasive' is the definition.
(I've seen this before)
'this person's about to enter a shade' is the wordplay.
'this person's' becomes 'im' (this person means the crossword setter themselves).
'about' says the letters should be written backwards.
'to enter' is an insertion indicator.
'a shade' becomes 'puce' (I've seen this before).
'im' written backwards gives 'mi'.
'mi' inserted inside 'puce' is 'PUMICE'.
(Other definitions for pumice that I've seen before include "Volcanic-rock scourer" , "Piece of volcanic rock used as an abrasive" , "Light, porous volcanic rock" , "Light porous stone used as polishing powder" , "Porous lava" .)