The most common and most likely answer to this crossword clue is the 11 letter word TONGUE-TIED
I've seen this crossword clue in The Times
T
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More clues leading to the result TONGUE-TIED
Buddy explains!
The straight part
We know that "lost for words" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lost for words = tongue-tied.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 TONGUE-TIED mean?
TONGUE-TIED adjective- Unable to express oneself clearly or fluently; at a loss for words.
- Suffering from tongue-tie or ankyloglossia.