Sink unblocker (7)
I believe the answer is:
plunger
'sink unblocker' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for plunger that I've seen before include "Rubber device for clearing blocked pipes" , "Plumber's friend" , "Hand tool used to clean clogged drains" , "Device for unblocking drains" , "Better" .)