The most common and most likely answer to this crossword clue is the 7 letter word BOBBING
I've seen this crossword clue in The Guardian
B
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B
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More clues leading to the result BOBBING
Buddy explains!
The straight part
We know that "going up and down" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case going up and down = bobbing.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 BOBBING mean?
BOBBING verb- To move gently and vertically, in either a single motion or repeatedly up and down, at or near the surface of a body of water, or similar medium.
- To move (something) as though it were bobbing in water.
- To curtsy.
- To strike with a quick, light blow; to tap.
- To cut (hair) into a bob haircut.
- To shorten by cutting; to dock; to crop
- To bobsleigh.
- The motion of something that bobs.