Barge to tie up, finding space to move in (9)
I believe the answer is:
elbowroom
'space to move in' is the definition.
(elbow room is space to move around in)
'barge to tie up' is the wordplay.
'barge' becomes 'elbow' (elbow can mean to barge or nudge out the way).
'to tie' becomes 'moor' (to moor a boat is to tie it up).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'moor' written backwards gives 'room'.
'elbow'+'room'='ELBOWROOM'
'finding' is the link.
(Other definitions for elbowroom that I've seen before include "Enough space to work or move in - flex arm" , "Bowl Romeo out to get some space" , "Space to manoeuvre - for arm-joint" , "Lower boom to make working space" , "Adequate work space" .)