Opposite number (11)
'opposite number' is the definition.
(synonyms)
This is all the clue.
(Other definitions for counterpart that I've seen before include "Match" , "Duplicate" , "See opposite number" , "Each of two copies of a legal document" .)
'opposite number' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for equal that I've seen before include "Commensurate" , "Level" , "Equivalent or equitable" , "The same in size, amount or value, etc." , "Evenly matched" .)