Series including Queen and Country (7)
I believe the answer is:
terrain
'country' is the definition.
(terrain means some land or country)
'series including queen' is the wordplay.
'series' becomes 'train' (train is a kind of series).
'including' means one lot of letters goes inside another.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'train' enclosing 'er' is 'TERRAIN'.
'and' is the link.
(Other definitions for terrain that I've seen before include "Landscape" , "Land (viewed tactically)" , "(Type of) ground" , "Stretch of land, emphasising natural features" , "Physical features of a tract of land" .)