Used in rolling Plasticine gel, ethylene's effective on a screen (9)
I believe the answer is:
telegenic
'effective on a screen' is the definition.
(telegenic means looking good on TV)
'used in rolling plasticine gel ethylene's' is the wordplay.
'rolling' is a reversal indicator.
'used in' indicates a hidden word.
'cinegelet' is hidden in the letters of 'plasticine gel ethylenes'.
'cinegelet' written backwards gives 'TELEGENIC'.
(Other definitions for telegenic that I've seen before include "Coming over on the tube" , "having broadcast appeal" , "attractive on screen" , "nice on screen too" , "appealing to viewers" .)