Clunking Gearbox

[Lou]

When I put the car into 1st gear before setting off it makes a clunking noise. I don't know if its doing it when driving and changing the gears though.
Any ideas what this could be?

 

[Gumby]

There's a ferret in your gearbox

 

[Turner]

There's a ferret in your gearbox

pmsl
but mine does this occasionlly when stationary then select 1st i sometimes get a sort of clunk,doesnt happen any other time thou??