Points about unusual Roman invaders (7)
I believe the answer is:
normans
'invaders' is the definition.
(norman conquest)
'points about unusual roman' is the wordplay.
'points' becomes 'ns' (N is an example**).
'about' is an insertion indicator.
'unusual' is an anagram indicator.
'roman' is an anagram of 'orman'.
'ns' placed around 'orman' is 'NORMANS'.
(Other definitions for normans that I've seen before include "They won the battle of Hastings" , "Our last successful invaders" , "some French people" , "Some Frenchmen" , "Invaders in 1066" .)