Man hard on a novice (3)
I believe the answer is:
hal
'man' is the definition.
(I've seen this before)
'hard on a novice' is the wordplay.
'hard' becomes 'h'.
'on' means one lot of letters go next to another.
'novice' becomes 'l' (abbreviation for Learner e.g. on UK cars**).
'h'+'a'+'l'='HAL'
(Other definitions for hal that I've seen before include "Man" , "Prince -, Falstaff's companion (Henry IV, Pt I)" , "Odyssean character" , "Falstaff's prince (H.IV)" , "royal prince" .)