The most common and most likely answer to this crossword clue is the 10 letter word DIAGNOSTIC
I've seen this crossword clue in The Guardian
D
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A
G
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T
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C
More clues leading to the result DIAGNOSTIC
- Policeman sceptical of outside agency helping solve problems
- Help rejected by old heretic? That’s symptomatic!
- Working out problem, I had backtracked, lacking certainty
- Analytical detective approaches questioning
- A sting? I, doc may be trying to analyse what’s wrong
- Detective professing limits to knowledge, but identifying problem
- Analytical, double skeptic?
- Analytical detective having some doubts
Buddy explains!

The straight part
We know that "symptomatic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case symptomatic = diagnostic.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 DIAGNOSTIC mean?
DIAGNOSTIC noun- Any technique used in medical diagnosis.
- Any tool or technique used to find the root of a problem.
- That by which anything is known; a symptom.
- Of, or relating to diagnosis.
- Characteristic of a particular disease.
- Serving to indicate or specify a particular item or thing within a group of similar things.