Teach about the Queen's country (7)
I believe the answer is:
terrain
'country' is the definition.
(thesaurus)
'teach about the queen's' is the wordplay.
'teach' becomes 'train' (training is a kind of teaching).
'about' means one lot of letters goes inside another.
'the queen' becomes 'er' (Elizabeth Regina).
'train' going around 'er' is 'TERRAIN'.
(Other definitions for terrain that I've seen before include "Trainer (anag) - land" , "Land of a particular type" , "Stretch of land of a particular sort" , "Tract of land with particular character" , "Ground (conditions)" .)