The most common and most likely answer to this crossword clue is the 12 letter word WALL-TO-WALL
I've seen this crossword clue in The Guardian
W
A
L
L
-
T
O
-
W
A
L
L
Buddy explains!

The straight part
We know that "Ubiquitous" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ubiquitous = wall-to-wall.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 WALL-TO-WALL mean?
WALL-TO-WALL adjective- (of carpeting) That covers all of the floor of a room.
- Pervasive, ubiquitous, or unremitting.
- (of a space) Full, crowded.