Line penned by novelist? I shouldn't think so! (6)
I believe the answer is:
hardly
'i shouldn't think so' is the definition.
I can't tell whether this definition defines the answer.
'line penned by novelist?' is the wordplay.
'line' becomes 'l' (used when specifying particular lines from a poem).
'penned by' is an insertion indicator (inserted letters are penned in).
'novelist?' becomes 'Hardy' (Hardy is a novelist).
'l' put inside 'hardy' is 'HARDLY'.
Can you help me to learn more?
(Other definitions for hardly that I've seen before include "With great difficulty" , "Barely, scarcely" , "Not quite "It seems unlikely!"" , "Almost not" , "Not much" .)