Unusually, oceans in south rise (9)
I believe the answer is:
ascension
'rise' is the definition.
(I know that rise can be written as ascension)
'unusually oceans in south' is the wordplay.
'unusually' indicates an anagram.
'south' becomes 's' (abbreviation).
'oceans'+'in'+'s'='oceansins'
'oceansins' anagrammed gives 'ASCENSION'.
(Other definitions for ascension that I've seen before include "religious feast" , "holy day" , "Canonises on Christ's way to heaven" , "Island in the South Atlantic" , "distance in hours measured by this, right?" .)