Listen anew to the guy in the back (6)
I believe the answer is:
rehear
'listen anew' is the definition.
(to hear something a second time)
'the guy in the back' is the wordplay.
'the guy' becomes 'he'.
'in' means one lot of letters goes inside another.
'the back' becomes 'rear' (synonyms).
'he' going inside 'rear' is 'REHEAR'.
'to' acts as a link.
(Other definitions for rehear that I've seen before include "Retry (a lawsuit)" , "be a sympathetic listener, not for the first time" , "Try again (in court)" , "Hold the trial again." .)