The most common and most likely answer to this crossword clue is the 3 plus 3 letter word YES MAN
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Buddy explains!
The straight part
We know that "One readily agrees" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one readily agrees = yes man.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 YES MAN mean?
YES MAN noun- A person who always agrees with their employer or superior.