Don't keep a promise to move a car from the garage? (4,3)
I believe the answer is:
back out
'don't keep a promise' is the definition.
I can't judge whether this defines the answer.
'move a car from the garage?' is the wordplay.
'move' becomes 'back' (backing is a kind of moving).
'a car from the garage?' becomes 'out' (I am not sure about this - if you are sure you should believe this answer much more).
'back'+'out'='BACK OUT'
'to' is the link.
Can you help me to learn more?
(Other definitions for back out that I've seen before include "Withdraw from agreement, or reverse car from driveway" , "Get cold feet" , "in the open air again?" , "Withdraw from a commitment" , "Withdraw from agreement in outback" .)