The most common and most likely answer to this crossword clue is the 10 letter word PATRONYMIC
I've seen this crossword clue in The Times
P
A
T
R
O
N
Y
M
I
C
More clues leading to the result PATRONYMIC
Buddy explains!
The straight part
We know that "O’Leary, perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case o’leary, perhaps = patronymic.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 PATRONYMIC mean?
PATRONYMIC noun- A name acquired from one's father.
- (by extension) A name acquired from one's father's, grandfather's or earlier (male) ancestor's first name. Some cultures use a patronymic where other cultures use a surname or family name; other cultures (like Russia) use both a patronymic and a surname.
- Derived from one's father.
- (by extension) Derived from one's ancestors.