Hear about every queen’s disloyalty (9)
I believe the answer is:
treachery
'disloyalty' is the definition.
(I know that treachery is a type of disloyalty)
'hear about every queen's' is the wordplay.
'hear' becomes 'try' (to hear or try a case in the legal sense).
'about' means one lot of letters goes inside another.
'every' becomes 'each' (synonyms).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'each'+'er'='eacher'
'try' enclosing 'eacher' is 'TREACHERY'.
(Other definitions for treachery that I've seen before include "lack of loyalty" , "Double-dealing" , "Two-timing" , "Deceptiveness" , "perfidious conduct" .)