Such as pertains to or constitutes the beginning or first steps; initial, introductory, opening, first.

Characterized by initiating; having the function, power, or faculty of beginning or originating something; of or relating to initiation, initiatory.

That breaks (through) the ice. Frequently in extended use, esp.: that breaks through cold reserve or stiffness, facilitating conversation or social…

with down, in, up, etc.