Assuming you are working in 2D (using CL_Sprites)

No, ClanLib does not have functions to handle Z-ordering of sprites.

This is because it should be a simple process, with the algorithm dependant on the application.

For example:
Find the maximum Z of the sprite set, draw it, and flag it drawn

Or create a linked list of sprites, linked by the Z position. Mantain each link when the Z position changes

Or bubble sort the list of sprites Z position

Or use C++ <sort> to sort the sprites Z position

Or use C qsort() to sort the sprites Z position

Or store the sprite in a Z position array from 0 to maximum depth (with a link list if the sprite is at same Z position). Scan the array from 0 to maximum depth when drawing