Transparency of a bit of playground equipment (5)
I believe the answer is:
'transparency' is the definition.
(slide is a kind of transparency)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for slide that I've seen before include "Decline", "Idles about on children's chute", "Picture", "Make mild fun of", "Microscope glass".)