The most common and most likely answer to this crossword clue is the 4 letter word WAVY
W
A
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More clues leading to the result WAVY
Buddy explains!

The straight part
We know that "Snow goose" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case snow goose = wavy.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does WAVY mean?
WAVY adjective- Rising or swelling in waves.
- Full of waves.
- Moving to and fro; undulating.
- Having wave-like shapes on its border or surface; waved.
- (of a margin) Moving up and down relative to the surface; undulate.
- Undé, in a wavy line; applied to ordinaries, or division lines.
- Drunk
- The snow goose (Chen caerulescens)