The Queen's upset about everybody, remember (6)
I believe the answer is:
recall
'remember' is the definition.
('recall' can be a synonym of 'remember')
'the queen's upset about everybody' is the wordplay.
'the queen' becomes 'er' (Elizabeth Regina).
'upset' shows that the letters should be reversed in order.
'about' becomes 'c' (abbreviation for 'circa'**).
'everybody' becomes 'all' (I've seen this before).
'er' reversed gives 're'.
're'+'c'+'all'='RECALL'
(Other definitions for recall that I've seen before include "Summon back as to memory" , "Don''t forget - come again" , "cancel" , "Recollect" , "Remember; demand back" .)