The most common and most likely answer to this crossword clue is the 3 plus 7 letter word THE PLANETS
I've seen this crossword clue in The Guardian
T
H
E
P
L
A
N
E
T
S
More clues leading to the result THE PLANETS
Buddy explains!
The straight part
We know that "Suite/probed by mariners and pioneers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case suite/probed by mariners and pioneers = the planets.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.