Knock off rapidly - lazily, in fact (4)
I believe the answer is:
idly
'lazily in fact' is the definition.
The definition and answer are not the same part of speech.
'knock off rapidly' is the wordplay.
'knock' becomes 'rap' (synonyms).
'off' is a deletion indicator.
'rapidly' with 'rap' taken out is 'IDLY'.
Can you help me to learn more?
(Other definitions for idly that I've seen before include "Lazily, without due attention" , "In a lazy manner" , "So lacking purpose" , "In a lazy fashion" , "How one stands by?" .)