Remove water from the yard, worried in case of disease (9)
I believe the answer is:
dehydrate
'remove water from' is the definition.
(I've seen this before)
'the yard worried in case of disease' is the wordplay.
'worried' indicates anagramming the letters.
'in' means one lot of letters goes inside another.
'case of' suggests removing the centre (outsides of).
'disease' with its centre taken out is 'de'.
'the'+'yard'='theyard'
'theyard' with letters rearranged gives 'ehydrat'.
'ehydrat' put inside 'de' is 'DEHYDRATE'.
(Other definitions for dehydrate that I've seen before include "Preserve by removing all liquid from" , "Remove water from" , "Drain" , "Remove moisture content from, dry out" , "Remove moisture from, make dry" .)