Two-sided (9)
I believe the answer is:
bilateral
I believe this clue is a double definition.
'two' is the first definition.
(thesaurus)
'sided' is the second definition.
(thesaurus)
(Other definitions for bilateral that I've seen before include "Two-sided" , "Undertaken by two parties" , "Involving two parties" , "involving more than one party?" , "involving two sides" .)