Accommodation that subsumes second accommodation (6)
I believe the answer is:
hostel
'accommodation' is the definition.
(I've seen this before)
'accommodation that subsumes second' is the wordplay.
'accommodation' becomes 'hotel' (type of accommodation).
'that subsumes' indicates putting letters inside (subsume can mean to absorb).
'second' becomes 's' (common abbreviation).
'hotel' going around 's' is 'HOSTEL'.
(Other definitions for hostel that I've seen before include "Temporary home for the hiker" , "Lodging establishment" , "B & B" , "Inn" , "Cheap accommodation for hikers" .)