Greek character past it, oddly (3)
I believe the answer is:
psi
'greek character' is the definition.
(letter from the Greek alphabet)
'past it oddly' is the wordplay.
'oddly' means one should take alternating letters.
'past'+'it'='pastit'
The alternating letters of 'pastit' are 'PSI'.
(Other definitions for psi that I've seen before include "Twenty-third letter of Greek alphabet" , "foreign letter" , "one employed by Socrates?" , "Greek letter; pressure unit" , "letter from abroad" .)