Cryptic crossword clue
Excellent teacher but an addict 9

The most common and most likely answer to this crossword clue is the 9 letter word CRACKHEAD

I've seen this crossword clue in Financial Times
C
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Buddy explains!

The straight part
We know that "an addict" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an addict = crackhead.
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 CRACKHEAD mean?

CRACKHEAD noun
  1. A person who is addicted to or regularly uses crack cocaine.
  2. Someone whose thinking makes no sense; a fool or an idiot.

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