Rule amended to include married primate (5)
I believe the answer is:
lemur
'primate' is the definition.
(I've seen this before)
'rule amended to include married' is the wordplay.
'amended' indicates an anagram.
'to include' means one lot of letters goes inside another.
'married' becomes 'm'.
'rule' is an anagram of 'leur'.
'leur' placed around 'm' is 'LEMUR'.
(Other definitions for lemur that I've seen before include "Arboreal primate native to Madagascar" , "Shade" , "Social climber" , "Madagascan monkey" , "Madagascan primate" .)