Melody imbues pitch occasionally (5)
I believe the answer is:
music
'melody' is the definition.
(I've seen this before)
'imbues pitch occasionally' is the wordplay.
'occasionally' means one should take alternating letters.
'imbues'+'pitch'='imbuespitch'
The alternating letters of 'imbuespitch' are 'MUSIC'.
(Other definitions for music that I've seen before include "Staff will support this" , "Vocal or instrumental sounds" , "Organised sound" , "melodies" , "Harmonious sound (generally!)" .)