The most common and most likely answer to this crossword clue is the 11 letter word ZOOPLANKTON
I've seen this crossword clue in The Times
Z
O
O
P
L
A
N
K
T
O
N
Buddy explains!
The straight part
We know that "Life drifting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case life drifting = zooplankton.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 ZOOPLANKTON mean?
ZOOPLANKTON noun- Free-floating small protozoa, crustaceans (such as krill), etc. and the eggs and larvae from larger animals.