Hit novel penned by young man (6)
I believe the answer is:
lashed
'hit' is the definition.
(I've seen this before)
'novel penned by young man' is the wordplay.
'novel' becomes 'she' (I've seen this before).
'penned by' means one lot of letters goes inside another.
'young man' becomes 'lad' (I've seen this before).
'she' inserted inside 'lad' is 'LASHED'.
(Other definitions for lashed that I've seen before include "severely punished" , "Flogged" , "Fastened securely" , "Tied -- beaten" , "Hit" .)