Adjust song (4)
I believe the answer is:
tune
I believe this is a double definition.
'adjust' is the first definition.
(tuning is a kind of adjusting)
'song' is the second definition.
(I know that tune is a type of song)
(Other definitions for tune that I've seen before include "Of engine, adjust to run smoothly" , "'He who pays the piper calls the ...'" , "strain" , "Song" , "Adjust a radio receiver to a frequency" .)