Pile of cash the queen's protection against a rainy day? (6)
I believe the answer is:
Here is my best explanation:
'protection against a rainy day?' is the definition.
I can't tell whether this definition defines the answer.
'pile of cash the queen's' is the wordplay.
'pile of cash' becomes 'wad'.
'the queen's' becomes 'ers' (Elizabeth Regina).
(Other definitions for waders that I've seen before include "Waterproof boots - shorebirds", "something worn by fishermen", "snipe, for instance", "Water birds", "Waterproof hip boots for anglers", "waterbirds?", "High boots for fishing", "Extended wellies", "Birds - boots" and "Snipes maybe".)