Space to move
'space to move' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for elbowroom that I've seen before include "Space to function" , "Bowl Romeo out to get some space" , "Enough space to work or move in - flex arm" , "Enough scope to function" , "Leeway" .)
(Other definitions for leeway that I've seen before include "Amount of freedom" , "Elbowroom" , "Allowance" , "Margin, latitude, room" , "Slack" .)