Country in which a unit is regrouped (7)
I believe the answer is:
tunisia
'country' is the definition.
(Tunisia is an example)
'a unit is regrouped' is the wordplay.
'regrouped' is an anagram indicator (I've seen 'regroup' mean this (I've seen this in other clues)).
'a'+'unit'+'is'='aunitis'
'aunitis' with letters rearranged gives 'TUNISIA'.
'in which' is the 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" .)