Primate with cross and crown (4)
I believe the answer is:
apex
'crown' is the definition.
(I've seen this in another clue)
'primate with cross' is the wordplay.
'primate' becomes 'ape' (large primate).
'with' means one lot of letters go next to another.
'cross' becomes 'x' (an X is a cross).
'ape'+'x'='APEX'
'and' acts as a link.
(Other definitions for apex that I've seen before include "Peak, vertex" , "Apogee, summit" , "The highest point or peak" , "Uppermost tip" , "Culmination" .)