User doesn't open skin care product (5)
I believe the answer is:
toner
'skin care product' is the definition.
(I've seen this in another clue)
'user doesn't open' is the wordplay.
'user' becomes 'stoner' (drug user).
'doesn't open' means to remove the first letter (the letter which opens the word is missing).
'stoner' with its initial letter taken away is 'TONER'.
(Other definitions for toner that I've seen before include "Powder used in printers" , "Powdered pigment used in laser printers" , "Material for printer" , "Skin improver" , "Chemical solution used to soften colours" .)