Tie up, seeing low resistance (4)
I believe the answer is:
moor
'tie up' is the definition.
(I've seen this before)
'low resistance' is the wordplay.
'low' becomes 'moo' ('moo' can be a synonym of 'low').
'resistance' becomes 'r' (abbreviation).
'moo'+'r'='MOOR'
'seeing' acts as a link.
(Other definitions for moor that I've seen before include "'On Ilka - - baht'at'" , "Secure ship with cables" , "African - wasteland" , "Open land - secure a boat - North African" , "Make fast a boat - open tract of rough ground" .)