One Greek character left in time to find another (7)
I believe the answer is:
epsilon
'find another' is the definition.
I can't judge whether this defines the answer.
'one greek character left in time' is the wordplay.
'one greek character' becomes 'psi' (letter from the Greek alphabet).
'left' becomes 'L' (common abbreviation).
'in' indicates putting letters inside.
'time' becomes 'eon' (eon is a kind of time).
'psi'+'l'='psil'
'psil' inserted inside 'eon' is 'EPSILON'.
'to' acts as a link.
(Other definitions for epsilon that I've seen before include "small number mispronounced, almost completely the wrong way round" , "5th letter of the Greek alphabet" , "Lose pin (anag.)" , "Greek letter - pinoles (anag)" , "foreign letter" .)