The most common and most likely answer to this crossword clue is the 5 letter word COCAS
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Buddy explains!
The straight part
We know that "South American shrubs" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case south american shrubs = cocas.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 COCAS mean?
COCAS noun- Any of the four cultivated plants which belong to the family Erythroxylaceae, native to western South America.
- The dried leaf of one of these plants, the South American shrub (Erythroxylum coca), widely cultivated in Andean countries, which is the source of cocaine.
- A pastry typically made and consumed in the Spanish Mediterranean coast.