Drive member (1) for clock movement comprising: a barrel (2, 2') comprising a drum (6, 6') mounted on an arbor (3) so that it can rotate with the abrbor (3) about an axis (4) when the drive member (1) is wound up; a main spring (8, 11) wound inside the barrel (2) and able to be wound up around the arbor (3) when the drive member (1) is wound up, and a core (17, 17') coaxial with and pivoting on the arbor (3); the exterior end (9, 13) of the spring (8, 11) being coupled to the drum (6, 6') and the interior end (10, 12) of the spring (8, 11) being coupled to the core (17, 17'); the exterior end (9, 13) of the spring (8, 11) is coupled to the drum (6, 6') by a first clamp (18) that is pivot mounted in the drum (6, 6') so that when the spring (8, 11)is unwound, the first clamp (18) pivots in such a way as to hold the exterior tuen of the first spring (8, 11) against the drum (6, 6') and when the spring (8, 11) is wound up, the first clamp (18) pivots towards the centre of the barrel (2) to follow the exterior turn of the spring (8, 11). The bending stresses in the spring are reduced.