The most common and most likely answer to this crossword clue is the 6 letter word DOOBRY
I've seen this crossword clue in The Guardian
D
O
O
B
R
Y
More clues leading to the result DOOBRY
Buddy explains!
The straight part
We know that "thing one cannot name" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case thing one cannot name = doobry.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 DOOBRY mean?
DOOBRY noun- Something not named; a thingy or whatsit.