Come into Rhine, swimming it (7)
I believe the answer is:
inherit
'come into' is the definition.
(synonyms)
'rhine swimming it' is the wordplay.
'swimming' indicates anagramming the letters.
'rhine' with letters rearranged gives 'inher'.
'inher'+'it'='INHERIT'
(Other definitions for inherit that I've seen before include "Come into (money)" , "Acquire from ancestors" , "Obtain as legacy" , "Receive as a legacy" , "Get what was left?" .)