What is "established" on an RNAV approach? I was looking at the RNAV (GPS) RWY 6 at 12J.  Thinking about my descent profile, I wondered when I could start my descent from my transition altitude if I was told to maintain an altitude until established.

For example, if the controller told me to "maintain 4000 until established," would I start descending after crossing the IAF and tear-dropping into the hold?  Would I start descending on the inbound leg?  Or, would I start descending after leaving the IAF inbound on the approach?

Edit:

This question assumes that a hold-in-lieu-of-procedure turn is required.  The question, really, is if a controller says "maintain 4000 until established," when can you start descending?  Can you descend as soon as you cross the IAF?
NOTE: This answer is specific to the United States as the question uses an example approach procedure from an airport in the United States. Procedures may vary for other nations. Consult the respective Aeronautical Information Publication for specific guidance.

As long as you hear the magic words "cleared  approach," you can begin your descent as soon as you cross the IAF the first time (while beginning your teardrop maneuver) and continue to descend to the minimum altitude while in the circuit, which is at or above 2000 for this particular procedure. 

Note that you MUST be on a published segment of the approach before making your descent, otherwise terrain clearance is not assured. 

The controller will expect you to proceed from the IF to the FAF after the first circuit is complete (a course reversal maneuver, if executed counts as the first circuit). You must advise the controller if additional circuits are required in order to lose altitude. Also, if the controller clears you for a "straight-in" approach and doing so would result in an excessive descent rate, it is incumbent upon you as the pilot to advise the controller that you are unable.

Reference: FAA JO 7110-615, Approach Clearance