Crack found in some of the Oslo tenement (4)
I believe the answer is:
slot
'crack' is the definition.
(thesaurus)
'some of the oslo tenement' is the wordplay.
'some of' says the answer is hidden in the clue.
'SLOT' is hidden within 'oslo tenement'.
'found in' acts as a link.
(Other definitions for slot that I've seen before include "Hole for e.g. coin" , "Narrow opening as in gaming machine" , "Opening (for coins)" , "Scheduled time -- aperture for coins" , "Scheduled time - hierarchical position" .)