His pa maybe like a primate (5)
I believe the answer is:
Here is my best explanation:
'like a primate' is the definition.
I can't judge whether this definition defines the answer.
'his pa maybe' is the subsidiary indication.
'maybe' indicates anagramming the letters.
'hispa' with letters rearranged gives 'apish'.
(Other definitions for apish that I've seen before include "Foolish; like a monkey", "Foolish; simian", "Foppish", "Stupid" and "Silly".)