Call used in boxing (4)
I believe the answer is:
ring
I believe this is a double definition.
'call' is the first definition.
(telephone call)
'boxing' is the second definition.
(thesaurus)
'used in' acts as a link.
(Other definitions for ring that I've seen before include "Buzz" , "Chime" , "sign of union?" , "Circular band; call" , "Make phone call" .)