The most common and most likely answer to this crossword clue is the 7 letter word TIP-TOP
I've seen this crossword clue in The Guardian
T
I
P
-
T
O
P
Buddy explains!

The straight part
We know that "excellent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case excellent = tip-top.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 TIP-TOP mean?
TIP-TOP adjective- Excellent
- The very topmost point.
- The highest or utmost degree; the best of anything.
- Excellently; in a first-rate manner.