Most of planet worried by Sweden's floods (9)
I believe the answer is:
saturates
'floods' is the definition.
(saturate can mean to flood or soak)
'most of planet worried by sweden's' is the wordplay.
'most of' means to remove the last letter.
'planet' becomes 'Saturn' (Saturn is an example).
'worried by' becomes 'ate' (something worrying may eat someone up. I am not sure about the 'by' bit.).
'sweden' becomes 's'.
'saturn' with its last letter taken off is 'satur'.
'satur'+'ate'+'s'='SATURATES'
(Other definitions for saturates that I've seen before include "Soaks" , "floods" .)