Old Arab nation included in small article (7)
I believe the answer is:
saracen
'old arab' is the definition.
(I've seen this before)
'nation included in small article' is the wordplay.
'nation' becomes 'race' (I've seen this before).
'included in' means one lot of letters goes inside another.
'small' becomes 's' (abbreviation - e.g. clothes size).
'article' becomes 'an' (indefinite article).
's'+'an'='san'
'race' placed within 'san' is 'SARACEN'.
(Other definitions for saracen that I've seen before include "Ear scan (anag.)" , "Muslim opposing the Crusades" , "Arab fighting the Crusades" , "Arab or Muslim at time of the Crusades" , "old Muslim back" .)