The most common and most likely answer to this crossword clue is the 11 letter word SMOKESCREEN
I've seen this crossword clue in Financial Times
S
M
O
K
E
S
C
R
E
E
N
More clues leading to the result SMOKESCREEN
Buddy explains!

The straight part
We know that "Cover" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cover = smokescreen.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 SMOKESCREEN mean?
SMOKESCREEN noun- Smoke used as a disguise, mask or cover, as of troops in battle.
- Anything used metaphorically to conceal or distract.