The most common and most likely answer to this crossword clue is the 13 letter word USER-FRIENDLY
I've seen this crossword clue in The Times
U
S
E
R
-
F
R
I
E
N
D
L
Y
More clues leading to the result USER-FRIENDLY
Buddy explains!

The straight part
We know that "Easy to understand" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case easy to understand = user-friendly.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 USER-FRIENDLY mean?
USER-FRIENDLY adjective- Designed to be easy for an untrained user to use.