How might one break an egg? Get cracking! (4,2,2)
I believe the answer is:
step on it
This clue is a double definition.
'how might one break an egg?' is the first definition.
(stepping on an egg would break it)
'get cracking' is the second definition.
(both can mean to move faster or act quickly)
(Other definitions for step on it that I've seen before include "to flatten an insect?" , "How might one kill an ant" , "to take advantage of escalating opportunity" , "be quicker" , "Go for speed" .)