Imitate kiss and climax (4)
I believe the answer is:
apex
'climax' is the definition.
(I've seen this before)
'imitate kiss' is the wordplay.
'imitate' becomes 'ape' (synonyms).
'kiss' becomes 'x'.
'ape'+'x'='APEX'
'and' acts as a link.
(Other definitions for apex that I've seen before include "Summit - pinnacle" , "Absolute peak" , "Uppermost point" , "Top point" , "crown" .)