The most common and most likely answer to this crossword clue is the 7 letter word LUNATIC
I've seen this crossword clue in The Daily Telegraph
L
U
N
A
T
I
C
More clues leading to the result LUNATIC
- Moonstruck in a cult after processing
- Nuts with plum and date, nice all shelled
- The smallest roomadvertised in Barking?
- Nut one Italian jerk on head for leering
- Extremely foolish for London’s earliest university to have Brown back in charge
- Nutter left girl with muscular spasm
- Eccentric in a cult, bonkers
- Eccentric learner driver, a Parisian with a twitch
- Crackpot embroiled in a cult
- Country not about to probe the stars, endlessly obsessed by the moon?
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 = lunatic.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 LUNATIC mean?
LUNATIC noun- An insane person.
- Crazed, mad, insane, demented.