The most common and most likely answer to this crossword clue is the 13 letter word THINGUMMYJIGS
I've seen this crossword clue in The Guardian
T
H
I
N
G
U
M
M
Y
J
I
G
S
Buddy explains!

The straight part
We know that "Unnamed items" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unnamed items = thingummyjigs.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.