Place containing tiny back room (6)
I believe the answer is:
leeway
'room' is the definition.
(thesaurus)
'place containing tiny back' is the wordplay.
'place' becomes 'lay' (laying is a kind of placing).
'containing' is an insertion indicator.
'tiny' becomes 'wee' (I've seen this before).
'back' says the letters should be written backwards.
'wee' back-to-front is 'eew'.
'lay' going around 'eew' is 'LEEWAY'.
(Other definitions for leeway that I've seen before include "play" , "Margin of tolerance" , "Drift - scope for action" , "Space for free movement" , "Amount of freedom" .)