Citroen Picasso clunking when turning corners?

Have it inspected at a tire and alignment shop. With no other clues or observations it's impossible to tell over a computer what the cause is. They'll look at ball joints, struts, anti-sway bar bushings, and control arm bushings. Other than ball joints and tie rod ends, clunks usually don't pose an immediate safety problem but they can adversely affect handling, braking, steering, and tire wear.