Standing for the Queen, rising and objecting to being under pressure (12)
I believe the answer is:
representing
'standing for' is the definition.
('represent' can be a synonym of 'stand for')
'the queen rising and objecting to being under pressure' is the wordplay.
'the queen rising' becomes 're' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'objecting to' becomes 'resenting' (to resent something is to object to it).
'being under' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'pressure' becomes 'p' (abbreviation).
'resenting' put after 'p' is 'presenting'.
're' next to 'presenting' is 'REPRESENTING'.
Can you help me to learn more?
(Other definitions for representing that I've seen before include "Speaking for" , "Acting for" .)