Roman brother killed flightless birds chasing rook (5)
I believe the answer is:
remus
'roman brother killed flightless' is the definition.
I can't tell whether this definition defines the answer.
'birds chasing rook' is the wordplay.
'birds' becomes 'emus' (emu is a kind of bird).
'chasing' means one lot of letters go next to another.
'rook' becomes 'R' (chess abbreviation).
'emus' after 'r' is 'REMUS'.
Can you help me to learn more?
(Other definitions for remus that I've seen before include "Brother of 15" , "Co-founder of Rome" , "US relative who did accounts" , "Brother of 24 across" , "murdered brother?" .)