Large number in French island are unemployed (4)
I believe the answer is:
idle
'unemployed' is the definition.
('idle' is associated in meaning with 'unemployed')
'large number in french island' is the wordplay.
'large number' becomes 'd'.
'in' indicates putting letters inside.
'french island' becomes 'ile' (French for 'island').
'd' put within 'ile' is 'IDLE'.
'are' acts as a link.
(Other definitions for idle that I've seen before include "Not in active use" , "goalless" , "Useless" , "not working in > lounge" , "without purpose" .)