Greek character's rank discussed (3)
I believe the answer is:
rho
'greek character's' is the definition.
(letter from the Greek alphabet)
'rank discussed' is the wordplay.
'rank' becomes 'row' (I've seen this in another clue).
'discussed' indicates a 'sounds like' (homophone) clue.
'row' sounds like 'RHO'.
(Other definitions for rho that I've seen before include "Sophocles character" , "letter to Athens" , "Greek P" , "Greek character" , "Seventeenth letter of the Greek alphabet" .)