Prepare to protect Queen and Country (7)
I believe the answer is:
terrain
'country' is the definition.
(terrain means some land or country)
'prepare to protect queen' is the wordplay.
'prepare' becomes 'train' (synonyms).
'to protect' means one lot of letters goes inside another.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'train' going around 'er' is 'TERRAIN'.
'and' acts as a link.
(Other definitions for terrain that I've seen before include "Land (as base for action)" , "Ground (conditions)" , "Ground - rare tin (anag)" , "Topography" , "Land with respect to its features" .)