Dry day — ready with the liquid (9)
I believe the answer is:
dehydrate
'dry' is the definition.
(I know that dehydrate is a type of dry)
'day ready with the liquid' is the wordplay.
'day' becomes 'd' (abbreviation for day).
'with' says to put letters next to each other.
'liquid' is an anagram indicator.
'ready' put after 'the' is 'theready'.
'theready' with letters rearranged gives 'ehydrate'.
'd'+'ehydrate'='DEHYDRATE'
(Other definitions for dehydrate that I've seen before include "Remove water from" , "Remove moisture from, make dry" , "Lose a lot of water" , "Drain" , "Preserve by removing all liquid from" .)