The most common and most likely answer to this crossword clue is the 4 plus 1 plus 7 letter word PLAY A BLINDER
I've seen this crossword clue in Independent
P
L
A
Y
A
B
L
I
N
D
E
R
Buddy explains!
The straight part
We know that "perform brilliantly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case perform brilliantly = play a blinder.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.