Anger that is consuming Romeo (3)
I believe the answer is:
ire
'anger' is the definition.
(ire is intense rage)
'that is consuming romeo' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'consuming' means one lot of letters goes inside another.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'ie' going around 'r' is 'IRE'.
(Other definitions for ire that I've seen before include "Strong feeling" , "passion" , "Paddy" , "Outrage" , "Annoyance, vexation" .)