Larry Harson is right; you should read Beneke's Physics Report. But I think I can make your reading easier by clearing up a misconception:

Renormalons (like instantons) aren't real things. They don't appear in the Lagrangian, and they don't correspond to any physical state. They are not auxiliary fields. What they are is divergences that show up when you use a particular approximation scheme. You could say, I suppose that the renormalons are the field configurations which lead to the divergences, but that's not quite the right spirit. If you do pure non-perturbative calcuations, you never see renormalons. They're an artefact of the perturbative approach.

Larry Harson is right; you should read Beneke's Physics Report. But I think I can make your reading easier by clearing up a misconception:

The name 'renormalon' is a bit misleading. Renormalons (like instantons) aren't real physical things. They don't appear in the Lagrangian, and they don't correspond to any physical state. They are not auxiliary fields. What they are is divergences that show up when you use a particular approximation scheme. You could say, I suppose that the renormalons are the field configurations which lead to the divergences, but that's not quite the right spirit. If you do pure non-perturbative calcuations, you never see renormalons. They're an artefact of the perturbative approach.