Punts over pastry to get bike going (4-5)
I believe the answer is:
kick-start
'punts over pastry to get bike going' is the definition.
I can't tell whether this definition defines the answer.
'pastry to get bike going' is the wordplay.
'pastry' becomes 'tart' (type of pastry).
'to get' says to put letters next to each other.
'bike going' becomes 'kicks' (I can't justify this - if you can you should give a lot more credence to this answer).
'tart' put after 'kicks' is 'KICK-START'.
Can you help me to learn more?
(Other definitions for kick-start that I've seen before include "Activate suddenly" , "make a good beginning" , "Provide an initial impetus" , "Activate (business or motorbike!)" , "Stimulate" .)