Ducks crossing lake hide (4)
I believe the answer is:
pelt
'hide' is the definition.
(synonyms)
'ducks crossing lake' is the wordplay.
'ducks' becomes 'pet' (both are terms of endearment).
'crossing' means one lot of letters goes inside another (to cross can mean to go over or around).
'lake' becomes 'L' (geographical abbreviation).
'pet' placed around 'l' is 'PELT'.
(Other definitions for pelt that I've seen before include "Skin of a fur-bearing mammal" , "what rain might do" , "Rain cats and dogs" , "Hide; rain" , "Hurl missiles at" .)