Feature includes a series (5)
I believe the answer is:
chain
'series' is the definition.
(I know that chain is a type of series)
'feature includes a' is the wordplay.
'feature' becomes 'chin' (facial feature).
'includes' is an insertion indicator.
'chin' going around 'a' is 'CHAIN'.
(Other definitions for chain that I've seen before include "a number of hotels" , "distance for a run?" , "unwelcome to house seeker" , "Group of atoms" , "Line of links" .)