The most common and most likely answer to this crossword clue is the 13 letter word APPROXIMATELY
I've seen this crossword clue in The Times
A
P
P
R
O
X
I
M
A
T
E
L
Y
More clues leading to the result APPROXIMATELY
Buddy explains!

The straight part
We know that "or so" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case or so = approximately.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 APPROXIMATELY mean?
APPROXIMATELY adverb- Imprecise but close to in quantity or amount.