Half of them agitate to be ruler (7)
I believe the answer is:
empress
'ruler' is the definition.
(female emperor)
'half of them agitate to be' is the wordplay.
I cannot quite see how this works, but
'them' could be 'em' (abbreviation) and 'em' is found within the answer.
'be' could be 'press' (pressing is a kind of being) and 'press' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for empress that I've seen before include "one married to ruler?" , "leading lady" , "She rules over many territories" , "Female ruler" , "Catherine the Great, for example" .)