Make-up of Universal screening 'ET'? (8)
I believe the answer is:
cosmetic
'make-up' is the definition.
(I've seen this before)
'universal screening 'et'?' is the wordplay.
'universal' becomes 'cosmic' (I've seen this before).
'screening' indicates putting letters inside (I've seen this in other clues).
'cosmic' enclosing 'et' is 'COSMETIC'.
'of' acts as a link.
(Other definitions for cosmetic that I've seen before include "Toiletry to beautify" , "Designed for appearance' sake" , "Aesthetic rather than necessary, surgery perhaps" , "With surface effect only" , "Good for appearances only" .)