Retinue protecting Queen and country (7)
I believe the answer is:
terrain
'country' is the definition.
(thesaurus)
'retinue protecting queen' is the wordplay.
'retinue' becomes 'train' (I've seen this before).
'protecting' is an insertion indicator.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'train' placed around 'er' is 'TERRAIN'.
'and' acts as a link.
(Other definitions for terrain that I've seen before include "Ground - rare tin (anag)" , "(Type of) ground" , "country" , "Stretch of land of a particular sort" , "Land (as base for action)" .)