Greeting current in river in renunciation (6)
I believe the answer is:
waiver
'renunciation' is the definition.
(I've seen this before)
'greeting current in river' is the wordplay.
'greeting' becomes 'wave' (I've seen this before).
'current' becomes 'I' (symbol for electric current).
'in' indicates putting letters inside.
'river' becomes 'r' (abbreviation for river).
'wave' enclosing 'i' is 'waive'.
'waive'+'r'='WAIVER'
'in' acts as a link.
(Other definitions for waiver that I've seen before include "Formal written statement of relinquishment" , "Document surrendering rights" , "Disclaimer of a legal right" , "Statement giving up a claim" , "Act of forgoing a right or claim" .)