Ancient greeting set in the earth in Neolithic site (7)
I believe the answer is:
avebury
'neolithic site' is the definition.
(neolithic monument)
'ancient greeting set in the earth' is the wordplay.
'ancient greeting' becomes 'ave' (greeting in Latin).
'set in the earth' becomes 'bury' (bury in earth).
'ave'+'bury'='AVEBURY'
'in' acts as a link.
(Other definitions for avebury that I've seen before include "Wiltshire stone ring" , "NT site near 9" , "Wiltshire stone circle" , "ancient ring of stones" , "Here one finds standing stones" .)