Strong check (7)
I believe the answer is:
staunch
I believe this is a double definition.
'strong' is the first definition.
(thesaurus)
'check' is the second definition.
(I've seen this before)
(Other definitions for staunch that I've seen before include "Stout" , "Loyal; restrict (a flow of blood)" , "Hearty" , "Dependable; stop (flow)" , "making it watertight" .)