The most common and most likely answer to this crossword clue is the 10 letter word SILVERWARE
I've seen this crossword clue in The Daily Telegraph
S
I
L
V
E
R
W
A
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E
Buddy explains!

The straight part
We know that "what’s in his trophy cabinet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what’s in his trophy cabinet = silverware.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 SILVERWARE mean?
SILVERWARE noun- Anything made from silver.
- Anything with a silvery colour.
- Knives, forks and spoons.
- Trophies, success in a competition.