First light turning ornamental cherry tree leaves red to begin with (5)
I believe the answer is:
sunup
'first light' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for sunup that I've seen before include "Literal version of dawn" , "Literal word for the dawn" , "Dawn (American)" , "time of day" , "early in America" .)