There is an 8-letter word hidden in this rebus.
The rebus is a riddle.
What is the 8 letter word?
EDIT: THAW should be TAHW, sorry 'bout that
What goes up when the rain comes down?
It is an:
WHAT is written bottom-to-top, RAIN is written top-to-bottom. That is the rebus itself.
The riddle itself is a chestnut.
Edit - interesting question raised by Preet in the comments, as
The first word is WAHT (or THAW) and not WHAT (or TAHW).