Times (long and short) come up with a letter (5)
I believe the answer is:
omega
'letter' is the definition.
(omega is a kind of letter of the alphabet)
I can't explain the rest of the clue.
(Other definitions for omega that I've seen before include "Greek long 'o'" , "end of series" , "Greek character symbolizing resistance" , "in Greece, the limit!" , "long letter" .)