The most common and most likely answer to this crossword clue is the 11 letter word CRACKERJACK
I've seen this crossword clue in Financial Times
C
R
A
C
K
E
R
J
A
C
K
More clues leading to the result CRACKERJACK
Buddy explains!

The straight part
We know that "something really good/t/h" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case something really good/t/h = crackerjack.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 CRACKERJACK mean?
CRACKERJACK noun- An exceptionally fine or excellent thing or person.
- An expert or top-rated individual (e.g., a marksman).
- Exceptionally fine or excellent; top-notch; high quality.
- Expert, top-rated or high-performing.
- (in the plural) The traditional blue uniforms of the enlisted men of the US Navy.
- A U.S. Navy sailor.
- Popcorn candied in molasses-flavored caramel and peanuts.
- Referring to clothing items (pants, jersey, collar) that constitute the traditional blue uniform of the enlisted men of the US Navy, following the sailor uniform worn by Sailor Jack on boxes of Cracker Jack snacks.