Unintentional sort of invader gets temporary accommodation (11)
I believe the answer is:
inadvertent
'unintentional' is the definition.
(I've seen this in another clue)
'sort of invader gets temporary accommodation' is the wordplay.
'sort of' indicates anagramming the letters.
'gets' says to put letters next to each other.
'temporary accommodation' becomes 'tent' (people stay in a tent temporarily).
'invader' is an anagram of 'inadver'.
'inadver'+'tent'='INADVERTENT'
(Other definitions for inadvertent that I've seen before include "Unthinking" , "Unintentional" , "unguarded" , "Accidental" , "without meaning" .)