The most common and most likely answer to this crossword clue is the 9 letter word ROUGHNECK
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Buddy explains!
The straight part
We know that "Work well in the main?/Yahoo!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case work well in the main?/yahoo! = roughneck.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 ROUGHNECK mean?
ROUGHNECK noun- Someone with rough manners; a rowdy or uncouth person.
- An ironworker; a dirty or low-paid worker, a labourer.
- A labourer on an oil rig.
- To work as a laborer on an oil rig