Specifically it refers to a dog pack. A pack of hunting dogs, has at its front, one dog that is the keenest and on top of the scent of the intended prey ( = intended goal or result). The rest follow the lead dog, rather than the scent of the prey.
To be ahead of the pack means that you are aware of the goal and that others can simply follow you although you will be the first to succeed in achieving that goal.
What does this idiom mean 
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