Strange going back inside Tangier office (7)
I believe the answer is:
foreign
'strange' is the definition.
(I know that strange can be written as foreign)
'going back inside tangier office' is the wordplay.
'going back' shows that the letters should be reversed in order.
'inside' indicates the answer is hidden within the clue.
'ngierof' is hidden within 'tangier office'.
'ngierof' reversed gives 'FOREIGN'.
(Other definitions for foreign that I've seen before include "Non-native" , "not appropriate" , "not typical" , "Not domestic" , "Of or from another country" .)