Keen listener, for example, held back (5)
I believe the answer is:
eager
'keen' is the definition.
(I've seen this in another clue)
'listener for example held back' is the wordplay.
'listener' becomes 'rae' (I am not sure about this - if you are sure you should believe this answer much more).
'for example' becomes 'e.g.' (short for 'exempli gratia', 'for example' in Latin).
'held' indicates putting letters inside.
'back' is a reversal indicator.
'rae' enclosing 'eg' is 'regae'.
'regae' written backwards gives 'EAGER'.
Can you help me to learn more?
(Other definitions for eager that I've seen before include "Anxious" , "Impatient" , "really keen" , "It's a bore" , "Zealous" .)