Musical effect that's a lot more fluttery? (7)

I believe the answer is:
tremolo
'musical effect' is the definition.
(I've seen this before)
'a lot more fluttery?' is the wordplay.
'lot more' can be anagrammed to 'TREMOLO'.
But, I am not clear how this is indicated.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for tremolo that I've seen before include "Wavering note" , "Musical wavering effect" , "Unsteady effect" , "Vocal vibrato -- lot more (anag)" , "Paganini's effect" .)
