The most common and most likely answer to this crossword clue is the 10 letter word PRODUCTIVE
I've seen this crossword clue in The Times
P
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Buddy explains!
The straight part
We know that "valuable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case valuable = productive.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 PRODUCTIVE mean?
PRODUCTIVE adjective- Capable of producing something, especially in abundance; fertile.
- Yielding good or useful results; constructive.
- Of, or relating to the creation of goods or services.
- (of an affix or word construction rule) Consistently applicable to any of an open set of words.
- Of a cough, producing mucus or sputum from the respiratory tract.
- Of inflammation, producing new tissue.
- A type of set of natural numbers, related to mathematical logic.