| STOPPAGE | Obstruction in a pipe (8) |
| BLOCKADE | Obstruction in a pipe (8) |
| CLOG | Obstruction in a pipe |
| STOPCOCK | A valve used to control the flow of a fluid in a pipe |
| BLOCKAGE | Obstruction, as in a pipe |
| BARRAGE | Artificial obstruction in a river (7) |
| BARRICADE | Obstruction in a bird race, possibly (9) |
| DAM | Manmade obstruction in a river |
| DAMUP | Create an obstruction, in a way |
| ROULETTE | Placing obstruction in the way is a chancy business (8) |
| BUOY | A distinctively shaped, coloured float, anchored to the bottom, for designating moorings, navigable channels or obstructions in a body of water (4) |
| PEDIMENT | I'm avoiding obstruction in part of temple |
| OFFSET | A counterbalance; a side shoot of a sempervivum for propagation; a mountain spur; or, a bend in a pipe (6) |
| BOURDON | The heaviest bell of a carillon; the drone of a bagpipe; or, derived from a French word meaning "bumblebee" or "buzz", a 16-foot stopped-flute in a pipe organ (7) |
| LOCK | Short section of a canal for raising or lowering a barge or narrowboat; or, an air-bubble in a pipe obstructing the flow of liquid (4) |
| CONSOLE | A kind of ornamental bracket; an ensemble of stops and keyboards in a pipe organ; or, a cabinet (7) |
| HOUSE | Accommodate a bend in a pipe |
| AIRLOCK | Bubble in a pipe causing an obstruction (7) |
| CLEANASAWHISTLE | Deal with obstruction in pipe, perhaps, with minimal mess |
| GALLSTONE | Obstruction in duct involving entire street in past (9) |
