Concert (3)
'concert' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gig that I've seen before include "A booking for musicians" , "Live performance by musicians" , "Palindromic one-night engagement" , "Perform live < in boat" , "Live performance; light two-wheeled carriage" .)
'concert' is the definition.
(to work in concert is to work in unison)
This is the entire clue.
(Other definitions for unison that I've seen before include "All singing the same note" , "There's agreement" , "Type of singing" , "Concord; a trade union" , "In agreement - like sound of choir" .)