Facial application: variety of dye injected into skin opening - revolutionary (3-4)
I believe the answer is:
eye-drop
'facial application variety' is the definition.
I know nothing about this answer so I can't tell whether this works.
'of dye injected into skin opening revolutionary' is the wordplay.
'of' indicates anagramming the letters (the answer comes from or 'of' the letters).
'injected into' is an insertion indicator.
'skin opening' becomes 'pore' (I've seen this in another clue).
'revolutionary' says the letters should be written backwards.
'pore' written backwards gives 'erop'.
'dye' anagrammed gives 'yed'.
'yed' inserted within 'erop' is 'EYE-DROP'.
Can you help me to learn more?
(Other definitions for eye-drop that I've seen before include "A tear (Shakespeare)" , "A poetical tear?" .)