I return and seem upset about Queen's demands (12)
I believe the answer is:
requirements
'demands' is the definition.
('requirement' can be a synonym of 'demand')
'i return and seem upset about queen's' is the wordplay.
'and' says to put letters next to each other (I've seen this in other clues).
'upset' indicates anagramming the letters.
'about' indicates putting letters inside.
'queen' becomes 'q' (abbreviation used in chess).
'return' after 'seem' is 'seemreturn'.
'i'+'seemreturn'='iseemreturn'
'iseemreturn' anagrammed gives 'reuirements'.
'reuirements' placed around 'q' is 'REQUIREMENTS'.
(Other definitions for requirements that I've seen before include "demands" , "Necessities" .)