Take control of French square (5)
I believe the answer is:
seize
This clue is a double definition.
'take control of' is the first definition.
(I've seen this in another clue)
'french square' is the second definition.
(French for 'sixteen', a square number)
(Other definitions for seize that I've seen before include "Take hold of, grab" , "Get hold of" , "Grab by force" , "Confiscate" , "Grasp forcibly" .)