Block up (8)
'block up' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for obstruct that I've seen before include "Block, hinder" , "Prevent or hinder movement" , "Stymie" , "Hinder or impede" , "Stop" .)
'block up' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dam that I've seen before include "Mad as an animal mum" , "A mad animal mother" , "Water barrier, quite mad" , "Reservoir barrier" , "Female parent of an animal, especially livestock" .)