The most common and most likely answer to this crossword clue is the 13 letter word CREEPY-CRAWLY
I've seen this crossword clue in Independent
C
R
E
E
P
Y
-
C
R
A
W
L
Y
More clues leading to the result CREEPY-CRAWLY
Buddy explains!
The straight part
We know that "mall and unpleasant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mall and unpleasant = creepy-crawly.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 CREEPY-CRAWLY mean?
CREEPY-CRAWLY noun- (trademark erosion) an automated suction pool cleaner.