The most common and most likely answer to this crossword clue is the 6 letter word ABLEST
I've seen this crossword clue in The Daily Telegraph
A
B
L
E
S
T
Buddy explains!

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 ABLEST mean?
ABLEST adjective- Easy to use.
- Suitable; competent.
- Liable to.
- Having the necessary powers or the needed resources to accomplish a task.
- Free from constraints preventing completion of task; permitted to; not prevented from.
- Having the physical strength; robust; healthy.
- Rich; well-to-do.
- Gifted with skill, intelligence, knowledge, or competence.
- Legally qualified or competent.
- Capable of performing all the requisite duties; as an able seaman.