The phrasal verb to 'crack on' means to continue doing or start to do something with urgency and determination especially after taking a break. Similar in meaning to 'get on with something' or to 'carry on with something'. 

1. With the match starting in twenty minutes, John knew he had better crack on with his homework if he was going to be finished it in time.
2. While the rest of the dinner party were sat at the dining table, Jane was in the kitchen, cracking on with the washing-up. 

1. We'd better crack on with that order, if we want to be able to dispatch it in time.
2. We have a lot to discuss in this meeting so let's crack on without wasting time.