Ban for greeting segment (8)
I believe the answer is:
prohibit
'ban' is the definition.
(I've seen this before)
'for greeting segment' is the wordplay.
'for' becomes 'pro' (I've seen this before).
'greeting' becomes 'hi' (hi is a kind of greeting).
'segment' becomes 'bit' (I've seen this before).
'pro'+'hi'+'bit'='PROHIBIT'
(Other definitions for prohibit that I've seen before include "Disallow" , "Forbid, ban" , "Ban; prevent" , "Stop" , "Bar" .)