Old queen welcomes Troy Romeo who'll say "I would die for you"? (6)
I believe the answer is:
martyr
'who'll say i would die for you?' is the definition.
I can't tell whether this definition defines the answer.
'old queen welcomes troy romeo' is the wordplay.
'old queen' becomes 'mary' (Mary I or Mary II. I am not sure about the 'old' bit.).
'welcomes' indicates putting letters inside (in sense of 'invites in').
'troy' becomes 't' (abbreviation - troy is a unit of weight).
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'mary' enclosing 't' is 'marty'.
'marty'+'r'='MARTYR'
Can you help me to learn more?
(Other definitions for martyr that I've seen before include "One who suffers death rather than renounce their religion" , "One suffers for the sake of principle" , "Victim for a cause" , "may be one hounded to death" , "One exaggerating suffering" .)