Energy learner exhibited? Nonsense (6)
I believe the answer is:
drivel
'nonsense' is the definition.
(drivel can mean nonsensical speech or writing)
'energy learner exhibited?' is the wordplay.
'energy' becomes 'drive' (drive can mean energy or enthusiasm).
'learner exhibited?' becomes 'L' (as in L-plates on a learner driver's car).
'drive'+'l'='DRIVEL'
(Other definitions for drivel that I've seen before include "Silly talk, sheer nonsense" , "Balls" , "Slaver" , "Silly talk, twaddle" , "Worthless, foolish nonsense" .)