State Pierre’s agreement to meet Welsh girl in Hollywood area (9)
I believe the answer is:
louisiana
'state' is the definition.
(I know that Louisiana is a American state)
'pierre's agreement to meet welsh girl in hollywood area' is the wordplay.
'pierre's agreement' becomes 'oui' ('yes' in French - Pierre is a French name).
'to meet' means one lot of letters go next to another.
'welsh girl' becomes 'sian' (common Welsh name).
'in' indicates putting letters inside.
'hollywood area' becomes 'LA'.
'oui'+'sian'='ouisian'
'ouisian' placed within 'la' is 'LOUISIANA'.
(Other definitions for louisiana that I've seen before include "American state, capital Baton Rouge" , "IOU a snail over in the US state" , "State named for French king" , "Southern United State on the Gulf of Mexico" , "US state, capital Baton Rouge" .)