The most common and most likely answer to this crossword clue is the 16 letter word HUNTER-GATHERERS
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Buddy explains!
The straight part
We know that "primitive folk" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case primitive folk = hunter-gatherers.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 HUNTER-GATHERERS mean?
HUNTER-GATHERERS noun- A member of a group of people who live by hunting animals and gathering edible plants for their main food sources, and who do not keep animals or farm land.