In accord with reggae in medley (8)
I believe the answer is:
agreeing
'in accord' is the definition.
(I've seen this before)
'with reggae in medley' is the wordplay.
'with' means one lot of letters go next to another.
'medley' indicates an anagram.
'reggae' put next to 'in' is 'reggaein'.
'reggaein' with letters rearranged gives 'AGREEING'.
(Other definitions for agreeing that I've seen before include "achieving harmony" , "Correspondent" , "At one" , "Holding same opinion" , "In concurrence" .)