Employ information technology in low-key, on-screen assistance (8)
I believe the answer is:
subtitle
'low-key on-screen assistance' is the definition.
I can't judge whether this definition defines the answer.
'employ information technology in' is the wordplay.
'employ information' becomes 'subtle' (I can't explain this - if you can you should believe this answer much more).
'technology' becomes 'it'.
'in' indicates putting letters inside.
'subtle' enclosing 'it' is 'SUBTITLE'.
Can you help me to learn more?
(Other definitions for subtitle that I've seen before include "Explanatory legend" , "Word found at bottom of movie or TV screen" , "Foreign dialogue translation shown on film" , "small print?" , "Translation of dialogue superimposed on film" .)