Kick-start (4)

I believe the answer is:

boot

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Other definitions for boot that I've seen before include "Amass and hide away" , "eg Wellington" , "Kick; footwear" , "Sturdy shoe; start (a computer)" , "Car luggage space; kick" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app