Rule out getting married to primate (5)
I believe the answer is:
lemur
'to primate' is the definition.
(lemur is a kind of primate)
'rule out getting married' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'getting' means one lot of letters goes inside another.
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'rule' is an anagram of 'leur'.
'leur' enclosing 'm' is 'LEMUR'.
(Other definitions for lemur that I've seen before include "Shade" , "A primate; sounds like a S. Am. city" , "Arboreal mammal common to Madagascar" , "Monkey-like creature of Madagascar" , "Arboreal animal" .)