Primate gets kiss at the top (4)
I believe the answer is:
apex
'the top' is the definition.
(apex is a top or peak)
'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' is the link.
(Other definitions for apex that I've seen before include "Point or summit" , "Tip -- top" , "Absolute peak" , "The highest point or pointed end" , "crown" .)