Hold on to the case (4)
I believe the answer is:
grip
This clue is a double definition.
'hold on to' is the first definition.
(thesaurus)
'case' is the second definition.
(I know that grip is a type of baggage)
'the' acts as a link.
(Other definitions for grip that I've seen before include "Stagehand" , "Purchase" , "Keep firm hold of" , "Control" , "Ditch" .)