"Begin cycling!" "I won't!" (4)
I believe the answer is:
nope
'begin cycling' is the definition.
I can't tell whether this definition defines the answer.
'i won't' is the wordplay.
I cannot quite understand how this works, but
'i won't' could be 'no' (refusal) and 'no' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nope that I've seen before include "You must be joking" , "I'm afraid not" , "Certainly not" , "definitely not!" , "not with stress" .)