Cryptic crossword clue
Plant originally found on isle brought into factory 7

The most common and most likely answer to this crossword clue is the 7 letter word MILFOIL

I've seen this crossword clue in Financial Times
M
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L
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L

Buddy explains!

The straight part
We know that "Plant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plant = milfoil.
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 MILFOIL mean?

MILFOIL noun
  1. Common yarrow, Achillea millefolium.
  2. Any of several similar pungent Eurasian herbs, of the genus Achillea
  3. Any plants of the genus Myriophyllum; water milfoil.

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