Seem to be a very quiet listener (6)
I believe the answer is:
appear
'seem to be' is the definition.
(I've seen this before)
'a very quiet listener' is the wordplay.
'very quiet' becomes 'pp'.
'listener' becomes 'ear' (I've seen this before).
'a'+'pp'+'ear'='APPEAR'
(Other definitions for appear that I've seen before include "Seem or materialise" , "Seem, look" , "Show up, become visible" , "become available" , "Become visible as ghost might" .)