Marine forced to stay (6)
I believe the answer is:
remain
'stay' is the definition.
(I know that stay can be written as remain)
'marine forced' is the wordplay.
'forced' indicates an anagram.
'marine' anagrammed gives 'REMAIN'.
'to' is the link.
(Other definitions for remain that I've seen before include "Stay on when others have left" , "stop behind?" , "Stay on after others have gone" , "Stay, don't go" , "Continue in position" .)