Act foolishly on your bike (4,2)
I believe the answer is:
beat it
'your bike' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'act foolishly' is the wordplay.
'act' becomes 'beat' (beat is a kind of act).
'foolishly' becomes 'it' (I am not sure about this - if you are sure you should believe this answer much more).
'beat'+'it'='BEAT IT'
'on' is the link.
Can you help me to learn more?
(Other definitions for beat it that I've seen before include "Clear off!" , "Get going" , "Sling your hook!" , "Scram, take a powder" , "fly away" .)