Couple; pair (3)
I believe the answer is:
duo
I believe this is a double definition.
'couple' is the first definition.
(I know that couple can be written as duo)
'pair' is the second definition.
(two people)
(Other definitions for duo that I've seen before include "Pair of performers" , "Music for two" , "They might play" , "Musical pair" , "Musical work for two" .)