Unusual tense used in this country’s English (5)
I believe the answer is:
outre
'unusual' is the definition.
(I've seen this before)
'tense used in this country's english' is the wordplay.
'tense' becomes 't' (abbreviation used in many dictionaries).
'used in' means one lot of letters goes inside another.
'this country' becomes 'our' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'english' becomes 'E' (abbreviation).
't' going within 'our' is 'outr'.
'outr'+'e'='OUTRE'
Can you help me to learn more?
(Other definitions for outre that I've seen before include "Eccentric or unseemly kind of route" , "Unusual, a bit shocking" , "Bizarre or eccentric in France" , "Unseemly route taken in France" , "flamboyant" .)