Create a vibrato effect as part of a score (6)
I believe the answer is:
quaver
I believe this is a double definition.
'create a vibrato effect' is the first definition.
(shake or tremble)
'part of a score' is the second definition.
(musical note)
'as' acts as a link.
(Other definitions for quaver that I've seen before include "Tremble - half a crotchet" , "Half-crotchet" , "Shake; a short note" , "Tremble; musical note" , "(Of voice) tremble" .)