Belief European is in temporary accommodation (5)
I believe the answer is:
tenet
'belief' is the definition.
(synonyms)
'european is in temporary accommodation' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'is in' is an insertion indicator.
'temporary accommodation' becomes 'tent' (I've seen this before).
'e' going inside 'tent' is 'TENET'.
(Other definitions for tenet that I've seen before include "you may believe in it" , "Article of faith; doctrine" , "Doctrine held to be true" , "That's the law" , "Belief - maxim" .)