Red Sea's in parts of the preparation (9)
I believe the answer is:
readiness
'the preparation' is the definition.
(thesaurus)
'red sea's in parts' is the wordplay.
'parts' indicates an anagram (the parts of the original word ordered differently).
'red'+'seas'+'in'='redseasin'
'redseasin' with letters rearranged gives 'READINESS'.
'of' acts as a link.
(Other definitions for readiness that I've seen before include "State of being prepared and willing" , "Immediate availability" , "State of preparedness" , "in prepared position" , "Inclination" .)