She knows what's said but doesn't listen (3,6)
I believe the answer is:
lip reader
'she' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for lip reader that I've seen before include "may well be deaf?" , "One, usually deaf, who uses sight to understand conversation" , "Interpreter of mouth movements" , "Person interpreting from mouth movements" , "One compensating for deafness" .)