Walk unsteadily - along the Dublin river? (6)
I believe the answer is:
dodder
'walk unsteadily along the dublin river?' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for dodder that I've seen before include "go falteringly" , "Tremble from age" , "Totter into the Dublin river" , "move unsteadily" , "Be decrepit in the Dublin river" .)