Two boys of the queen (5)
I believe the answer is:
royal
'queen' is the definition.
(I've seen this before)
'two boys' is the wordplay.
'two boys' means two substitutions for 'boy'.
'boy' becomes 'roy' ().
'boy' becomes 'al'.
'roy'+'al'='ROYAL'
'of the' acts as a link.
(Other definitions for royal that I've seen before include "What we may get used for individual" , "Relating to king/queen" , "Befitting a monarch" , "This blue is deep and vivid" , "First-rate" .)