Was mistaken queen embarrassed? (5)
I believe the answer is:
erred
'was mistaken' is the definition.
(I've seen this before)
'queen embarrassed?' is the wordplay.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'embarrassed?' becomes 'red' (someone may blush or go red when embarrassed).
'er'+'red'='ERRED'
(Other definitions for erred that I've seen before include "Made mistakes" , "Committed a sin" , "Made mistake, was incorrect" , "Gone astray!" , "slipped up" .)