For most people, I think the sound /ð/ at the end of “with” is probably the tricky part here. Make sure the front of your tongue is touching your top front teeth, then blow air through. You need to use your voice too. You can feel if you are using your voice by placing your fingers on your throat. When you use your voice, you’ll feel the vibration. The n of “on” could be pronounced as /m/ making the transition to /w/ easier.Finally, the t can also be pronounced as a glottal stop. (See notes on “Come off it!”)
This phrase means “Hurry up!”, or “Hurry up and do it!”.