Primate gets kiss at summit (4)
I believe the answer is:
apex
'summit' is the definition.
(I've seen this before)
'primate gets kiss' is the wordplay.
'primate' becomes 'ape' (large primate).
'gets' means one lot of letters go next to another.
'kiss' becomes 'x' (X can represent a kiss).
'ape'+'x'='APEX'
'at' acts as a link.
(Other definitions for apex that I've seen before include "Topmost point" , "Top point" , "white collar union" , "Tip -- top" , "Acme" .)