Tie up in the back-room (4)
I believe the answer is:
moor
'tie up' is the definition.
(as in mooring a boat)
'back-room' is the wordplay.
'back' is a reversal indicator.
'room' in reverse letter order is 'MOOR'.
'in the' is the link.
(Other definitions for moor that I've seen before include "Use ropes to secure" , "Someone like Othello" , "The Battle of Marston - -" , "eg Ilkley, Othello" , "Open upland; tie up boat" .)