Greek character gets stood up two times (5)
I believe the answer is:
omega
'greek character' is the definition.
(letter from the Greek alphabet)
'stood up two times' is the wordplay.
'two times' means two replacements for 'time'.
'stood up' shows that the letters should be reversed in order (in a down clue, letters go up).
'time' becomes 'age' (an age is a period of time).
'time' becomes 'mo' (I am not sure about this - if you are sure you should believe this answer much more).
'age'+'mo'='agemo'
'agemo' back-to-front is 'OMEGA'.
'gets' is the link.
Can you help me to learn more?
(Other definitions for omega that I've seen before include "Athenian character" , "symbol of resistance?" , "Traditional story" , "Consummation" , "Final outcome" .)