Don't insist on greeting being heard (5)
I believe the answer is:
waive
'don't insist on' is the definition.
(I've seen this before)
'greeting being heard' is the wordplay.
'greeting' becomes 'wave' (I've seen this before).
'being heard' indicates a 'sounds like' (homophone) clue.
'wave' is a homophone of 'WAIVE'.
(Other definitions for waive that I've seen before include "Not insist on (claim)" , "Relinquish" , "Refrain from insisting on right or privilege" , "Surrender" , "Give up" .)