Reach a swirling river (6)
I believe the answer is:
arrive
'reach' is the definition.
(thesaurus)
'a swirling river' is the wordplay.
'swirling' indicates an anagram.
'river' with letters rearranged gives 'rrive'.
'a'+'rrive'='ARRIVE'
(Other definitions for arrive that I've seen before include "Come to; succeed" , "Turn up" , "(Of time) come about" , "Reach destination or desired position" , "Reach intended destination" .)