The most common and most likely answer to this crossword clue is the 6 letter word PARTED
I've seen this crossword clue in The Daily Telegraph
P
A
R
T
E
D
More clues leading to the result PARTED
Buddy explains!

The straight part
We know that "Left" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case left = parted.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 PARTED mean?
PARTED verb- To leave the company of.
- To cut hair with a parting; shed.
- To divide in two.
- To be divided in two or separated; shed.
- To divide up; to share.
- To have a part or share; to partake.
- To separate or disunite; to remove from contact or contiguity; to sunder.
- To hold apart; to stand or intervene between.
- To separate by a process of extraction, elimination, or secretion.
- To leave; to quit.
- To leave (an IRC channel).
- Separated; taken asunder.
- (in combination) Having the specified number of parts.
- Deeply cleft.