The most common and most likely answer to this crossword clue is the 7 letter word RADICES
I've seen this crossword clue in The Guardian
R
A
D
I
C
E
S
Buddy explains!
The straight part
We know that "Roots" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case roots = radices.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 RADICES mean?
RADICES noun- A root.
- A primitive word, from which other words may be derived.
- The number of distinct symbols used to represent numbers in a particular base, as ten for decimal.