Expel refugee at first detained in terminus (6)
I believe the answer is:
deport
'expel' is the definition.
(I know that deport is a more specific form of the action expel)
'refugee at first detained in terminus' is the wordplay.
'at first' indicates taking the first letters.
'detained in' indicates putting letters inside.
'terminus' becomes 'depot' (synonyms).
The first letter of 'refugee' is 'r'.
'r' going within 'depot' is 'DEPORT'.
(Other definitions for deport that I've seen before include "Eject from country" , "conduct rarely seen nowadays?" , "Remove an unwanted person from a country" , "Expel as an undesirable alien" , "Expel from country - not a citizen" .)