Rapidly knock off, thus showing laziness (4)
I believe the answer is:
idly
'thus showing laziness' is the definition.
I can't judge whether this definition defines the answer.
'rapidly knock off' is the wordplay.
'knock' becomes 'rap' (synonyms).
'off' is a deletion indicator (some letters taken off).
'rapidly' with 'rap' removed is 'IDLY'.
Can you help me to learn more?
(Other definitions for idly that I've seen before include "In a lazy fashion" , "How people may stand by" , "without purpose" , "In a lazy manner" , "without good reason" .)