See what's being said of cheek scan (3-4)
I believe the answer is:
lip-read
'see' is the definition.
(I know that lip-read is a more specific form of the action read)
'being said of cheek scan' is the wordplay.
I cannot really see how this works, but
'cheek' could be 'lip' (both can mean insolence or rudeness) and 'lip' is found in the answer.
'scan' could be 'read' (synonyms) and 'read' is found in the answer.
No letters remain.
This explanation may well be incorrect...
'what's' is the link.
Can you help me to learn more?
(Other definitions for lip-read that I've seen before include "Interpret someone''s words when deaf" , "Understand by watching (a person) speak" , "Dire pal can interpret mouth movements as words" , "Understand without hearing" , "How to "hear" when deaf" .)