The most common and most likely answer to this crossword clue is the 6 plus 5 letter word PATRON SAINT
I've seen this crossword clue in The Sunday Telegraph
P
A
T
R
O
N
S
A
I
N
T
More clues leading to the result PATRON SAINT
- Supportive influence that may be not partisan
- Virgin Mary in France possibly playing nation's part
- Religious symbol, where dancing or pants are not common
- Part played by nations – could be protector
- Country’s defender isn’t after pants or elastic
- Spot on! Queen recast nation’s figurehead
- Good person taking nation’s part, in a way
- Son messing with art covered in dye — George is that?
- George of England perhaps, unlikely star in panto
- Andrew perhaps is not partisan in dispute
Buddy explains!
The straight part
We know that "Nikolaos of Greece, say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nikolaos of greece, say = patron saint.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.