Container in grate (3)
I believe the answer is:
jar
I believe this is a double definition.
'container' is the first definition.
(jar is a kind of container)
'grate' is the second definition.
(thesaurus)
'in' is the link.
(Other definitions for jar that I've seen before include "Disturbing effect" , "Container; be incongruous" , "Storage container" , "Vessel; sudden impact" , "Glass of beer; clash" .)