Exploits the U.S. marines heartlessly! (4)
I believe the answer is:
uses
'exploits' is the definition.
(use is a kind of exploit)
'u s marines heartlessly' is the wordplay.
'marines heartlessly' becomes 'es' (I can't explain this - if you can you should give a lot more credence to this answer).
'u'+'s'+'es'='USES'
'the' is the link.
Can you help me to learn more?
(Other definitions for uses that I've seen before include "Customs" , "Purposes; consumes" , "Puts into service" , "Utilises" , "Exercises" .)
