The most common and most likely answer to this crossword clue is the 4 plus 2 plus 3 plus 6 letter word BATS IN THE BELFRY
I've seen this crossword clue in The Guardian
B
A
T
S
I
N
T
H
E
B
E
L
F
R
Y
More clues leading to the result BATS IN THE BELFRY
Buddy explains!
The straight part
We know that "One’s mad to have these" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one’s mad to have these = bats in the belfry.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.