The most common and most likely answer to this crossword clue is the 8 letter word DIAGNOSE
I've seen this crossword clue in The Daily Telegraph
D
I
A
G
N
O
S
E
More clues leading to the result DIAGNOSE
- Recognise complaint raising appropriation of tune by on-line charity
- A doctor might mix a gin in the medicine
- Identify charity backing good runner
- Identify the problem — gain ground feeding prescribed medicine
- Identify potential gain in some medicine
- Identify area in mine with smell
- A doctor might mix a gin in medicine
- Identify mistake in dosage
- Agonised about how to identify a complaint
- Agonised over how to find fault
Buddy explains!

The straight part
We know that "A doctor might" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a doctor might = diagnose.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 DIAGNOSE mean?
DIAGNOSE verb- To determine which disease is causing a sick person's signs and symptoms; to find the diagnosis.
- (by extension) To determine the cause of a problem.