Space where dock set up (4)
I believe the answer is:
room
'space' is the definition.
(enough space or room to do something)
'dock set up' is the wordplay.
'dock' becomes 'moor' (I've seen this in another clue).
'set up' is a reversal indicator (in a down clue, letters go up).
'moor' written backwards gives 'ROOM'.
'where' is the link.
(Other definitions for room that I've seen before include "Space; part of building" , "basic accommodation" , "See 17" , "Enclosed space in a building" , "Latitude" .)