Waterfall that is right for former prince? (7)
I believe the answer is:
rainier
'former prince?' is the definition.
(I've seen this before)
'waterfall that is right' is the wordplay.
'waterfall' becomes 'rain' (rain is water falling down).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'right' becomes 'r' (common abbreviation).
'rain'+'ie'+'r'='RAINIER'
'for' acts as a link.
(Other definitions for rainier that I've seen before include "More wet - Monaco's late prince" , "more cats and dogs?" , "Former prince of Monaco" , "Prince . . . . . . . rules Monaco" , "Peak in Washington" .)