Sealing stuff (4)
I believe the answer is:
tape
'sealing stuff' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tape that I've seen before include "Measure" , "The winning runner breasts the ...." , "This is often stretched across the finishing line of race" , "Strip of material (that might be red!)" , "Common medium for recording" .)