Impressing me, country reversed rule (7)
I believe the answer is:
regimen
'rule' is the definition.
(thesaurus)
'impressing me country reversed' is the wordplay.
'impressing' means one lot of letters goes inside another (impress historically meant to conscript).
'country' becomes 'niger' (Niger is an example**).
'reversed' says the letters should be written backwards.
'niger' reversed gives 'regin'.
'me' put within 'regin' is 'REGIMEN'.
(Other definitions for regimen that I've seen before include "Mere gin for a course of treatment" , "(In medicine) a systematic plan for therapy" , "System of diet etc" , "Therapeutic course of treatment" , "Therapeutic programme (of diet and exercise)" .)