The most common and most likely answer to this crossword clue is the 10 letter word DIVESTMENT
I've seen this crossword clue in The Guardian
D
I
V
E
S
T
M
E
N
T
Buddy explains!

The straight part
We know that "for selling off" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case for selling off = divestment.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.
Crossword Answer definitions
DIVESTMENT noun- The sale or other disposal of some kind of asset.