Greek character has something to bet that needs parking (3)
I believe the answer is:
chi
'greek character' is the definition.
(letter from the Greek alphabet)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for chi that I've seen before include "T'ai -, martial art" , "Twenty-second Greek letter" , "Mental projection" , "Greek letter; Chinese life force" , "character in Thessaloniki" .)