Country in which a unit is regrouped (7)
I believe the answer is:
tunisia
'country' is the definition.
(I know that Tunisia is a country)
'a unit is regrouped' is the wordplay.
'regrouped' indicates an anagram (I've seen 'regroup' mean this (I've seen this in other clues)).
'a'+'unit'+'is'='aunitis'
'aunitis' anagrammed gives 'TUNISIA'.
'in which' acts as a link.
(Other definitions for tunisia that I've seen before include "Land" , "Republic in northwestern Africa" , "African state" , "Country between Algeria/Libya" , "Country in North Africa" .)