Controlling woman curtailed legal process in demonstration (9)
I believe the answer is:
matriarch
'controlling woman' is the definition.
(a matriarch is a woman in control)
'curtailed legal process in demonstration' is the wordplay.
'curtailed' means to remove the last letter.
'legal process' becomes 'trial' (trial in a court).
'in' indicates putting letters inside.
'demonstration' becomes 'march' (type of protest or demonstration).
'trial' with its last letter taken away is 'tria'.
'tria' placed into 'march' is 'MATRIARCH'.
(Other definitions for matriarch that I've seen before include "Very old or venerable woman" , "Dominating female" , "Dominant female" , "Female head of a family or tribe" , "Woman dominating" .)