Seem to be a listener, keeping very quiet (6)
I believe the answer is:
'seem to be' is the definition.
(I've seen this before)
'a listener keeping very quiet' is the wordplay.
'listener' becomes 'ear' (I've seen this before).
'keeping' indicates putting letters inside.
'very quiet' becomes 'pp'.
'aear' going around 'pp' is 'APPEAR'.
(Other definitions for appear that I've seen before include "Present oneself" , "Turn up" , "Become visible as ghost might" , "Perform" , "Show up like ghost" .)