The most common and most likely answer to this crossword clue is the 8 letter word SHAMROCK
I've seen this crossword clue in The Times
S
H
A
M
R
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K
More clues leading to the result SHAMROCK
- Imitation diamond that’s sported by an Irishman?
- National emblem a rhinestone?
- Plant using fake diamond maybe
- National emblem made of imitation stone?
- Scare about ram running amok in plant
- Is it paste produced in this plant?
- Perhaps a rhinestone is a national symbol
- Rhinestone, a national symbol
- Plant fake diamond?
- Plant marrow periodically in hut
Buddy explains!

The straight part
We know that "National emblem" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case national emblem = shamrock.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 SHAMROCK mean?
SHAMROCK noun- The trefoil leaf of any small clover, especially Trifolium repens, or such a leaf from a clover-like plant, commonly used as a symbol of Ireland.
- Any of several small plants, forms of clover, with trefoil leaves, especially Trifolium repens.