The most common and most likely answer to this crossword clue is the 5 plus 2 plus 5 letter word BORED TO TEARS
I've seen this crossword clue in The Daily Telegraph
B
O
R
E
D
T
O
T
E
A
R
S
More clues leading to the result BORED TO TEARS
Buddy explains!
The straight part
We know that "showing no interest whatever" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case showing no interest whatever = bored to tears.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.