Phrase that’s chanted in Roman tragedy (6)
I believe the answer is:
mantra
'phrase that's chanted' is the definition.
'in roman tragedy' is the wordplay.
'in' indicates the answer is hidden within the clue.
'MANTRA' is hidden in the letters of 'roman tragedy'.
(Other definitions for mantra that I've seen before include "Something said to focus concentration" , "that > may be repeated in reflection" , "Phrase repeated as aid to meditation in Buddhism" , "Chanted phrase" , "Slogan; refrain" .)