The most common and most likely answer to this crossword clue is the 3 letter word ODD
I've seen this crossword clue in The Times
O
D
D
More clues leading to the result ODD
- Those letters of Scot are so curious
- Funny comedian ignoring the first of three daughters
- Unusual old doctor of religion
- Queen upset losing island rum
- Rum starts off old drunkard's dipsomania
- Eccentric old theologian
- Like 9 and 0, for instance — neither one thing nor another to Shakespeare
- Overdose on drink, principally rum
- Rum included in good diet
- Occasional outswinging deliveries discombobulating openers
Buddy explains!

The straight part
We know that "Eccentric" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case eccentric = odd.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 ODD mean?
ODD noun- (diminutive) An odd number.
- Something left over, not forming part of a set.
- Differing from what is usual, ordinary or expected.
- Without a corresponding mate in a pair or set; unmatched; (of a pair or set) mismatched.
- Left over, remaining after the rest have been paired or grouped.
- Left over or remaining (as a small amount) after counting, payment, etc.
- Scattered; occasional, infrequent; not forming part of a set or pattern.
- Not regular or planned.
- Used or employed for odd jobs.
- Numerically indivisible by two.
- Numbered with an odd number.
- (in combination with a number) About, approximately; somewhat more than (an approximated round number).
- Out of the way, secluded.
- On the left.
- Singular in excellence; matchless; peerless; outstanding.