Fisherman's boot (5)
I believe the answer is:
'fisherman's boot' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for wader that I've seen before include "Long-legged shore bird" , "Snipe maybe" , "Eg, sandpiper or plover" , "High waterproof boot" , "crane, perhaps" .)