Definitely not name of listener (2,4)
I believe the answer is:
no fear
'definitely not' is the definition.
(I've seen this before)
'name of listener' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'listener' becomes 'ear' (I've seen this before).
'n'+'of'+'ear'='NO FEAR'
(Other definitions for no fear that I've seen before include "Never" , "Informally, certainly not., who's afraid" , "Definitely not (informal)" , "What 7 [INTREPID] person will have" , "Informally, not likely to do - who's afraid?" .)