Held back in Belfast so organised place to sleep (5)
I believe the answer is:
roost
'sleep' is the definition.
(for birds, to roost is to settle down to sleep)
'held back in belfast so organised place' is the wordplay.
'held back' shows that the letters should be reversed in order.
'in' indicates the answer is hidden within the clue.
'tsoor' is hidden within 'belfast so organised place'.
'tsoor' written backwards gives 'ROOST'.
'to' is the link.
(Other definitions for roost that I've seen before include "Perch on a branch" , "Hen house; perch" , "In Orkney, the current" , "Bird's shelter" , "suitable sleeping-place" .)