Jim Macklin wrote:
You are officially "in the hold" the first time you cross
the fix {in this case the NDB or a VOR} and if you're
established on the inbound course after intercepting the
course after your teardrop or direct entry, you can proceed
inbound or you have the option at pilot's discretion to go
around until you're established and ready.

If the hold is for course reversal in lieu of a procedure turn (bold
type, and you have been cleared for the approach, you are only allowed
one circuit in the hold unless you obtain a clearance for more than one
circuit.

(AIM 5-4-9 a 4)