Placebo, with time, almost played in harmony (10)
I believe the answer is:
compatible
'in harmony' is the definition.
(I've seen this before)
'placebo with time almost played' is the wordplay.
'with' says to put letters next to each other.
'almost' means to remove the last letter (most of the word but not all of it).
'played' indicates anagramming the letters.
'time' with its final letter removed is 'tim'.
'placebo' after 'tim' is 'timplacebo'.
'timplacebo' anagrammed gives 'COMPATIBLE'.
(Other definitions for compatible that I've seen before include "in harmony" , "Well suited" , "Able to coexist happily" .)