Web-footed birds (5)
'web-footed birds' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for geese that I've seen before include "Long-necked, migratory aquatic birds" , "Domesticated birds" , "Grey-lags" , "Large farm birds" , "Six of these are 'a-laying' on 31 December" .)
(Other definitions for ducks that I've seen before include "Eg, mallards" , "Teal, wigeon etc" , "Evades" , "Water birds; zero scores" , "Birds - term of endearment (informal)" .)