The most common and most likely answer to this crossword clue is the 9 letter word PRACTISED
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result PRACTISED
Buddy explains!
The straight part
We know that "Perfectly proficient" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case perfectly proficient = practised.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 PRACTISED mean?
PRACTISED verb- To repeat (an activity) as a way of improving one's skill in that activity.
- To repeat an activity in this way.
- To perform or observe in a habitual fashion.
- To pursue (a career, especially law, fine art or medicine).
- To conspire.
- To put into practice; to carry out; to act upon; to commit; to execute; to do.
- To make use of; to employ.
- To teach or accustom by practice; to train.
- Skillful, proficient, knowledgeable or expert as a result of practice