An indexable cutting insert for a milling tool includes an upper side defining an upper extension plane and a lower side defining a lower extension plane parallel to the upper extension plane. A side surface connects the upper side and the lower side, the side surface including a plurality of upper main clearance surfaces and secondary clearance surfaces. At least six identical and alternately usable upper cutting edges extend around the upper side. Each cutting edge has a chip removing main cutting edge portion and at least one secondary cutting edge portion. The main cutting edge portion is formed in a transition between the upper side and one of the upper main clearance surfaces. The secondary cutting edge portion is formed in a transition between the upper side and one of the secondary clearance surfaces between two main cutting edge portions. The upper main clearance surfaces are formed at an obtuse inner angle α with respect to the upper extension plane as seen in side elevation view.