Sink, perhaps, in event (7)
I believe the answer is:
fixture
I believe this is a double definition.
'sink perhaps' is the first definition.
(sink is a kind of fixture)
'event' is the second definition.
(thesaurus)
'in' is the link.
(Other definitions for fixture that I've seen before include "Sports match" , "Arranged sporting event cannot be moved" , "Attachment" , "Appointment for match or thing firmly in place" .)