The most common and most likely answer to this crossword clue is the 4 letter word SOLO
I've seen this crossword clue in The Daily Telegraph
S
O
L
O
More clues leading to the result SOLO
- Performance in Oslo slammed
- So Long, half cut single
- Aria, say, very much for bass? Not quite
- Individual entrées of salmon on Lyonnaise onions
- Card game very basic, did you say?
- But this game is not played by one alone
- Knight leaves without delay to tour Luxembourg unaccompanied
- Stokes’s last over — look at that individual performance!
- A singular performance
- How one flies extremely close to ground, mostly
Buddy explains!

The straight part
We know that "A singular performance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a singular performance = solo.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 SOLO mean?
SOLO noun- A piece of music for one performer.
- A job or performance done by one person alone.
- (games) A card game similar to whist in which each player plays against the others in turn without a partner
- A single shot of espresso.
- An instance of soloing the football.
- To perform a solo.
- To perform something in the absence of anyone else.
- To drop the ball and then toe-kick it upward into the hands.
- Without a companion or instructor.
- Of, or relating to, a musical solo.
- Alone, without a companion.