Guitarist's effect gets lot more rocking (7)
I believe the answer is:
tremolo
'guitarist's effect' is the definition.
'tremolo' can be an answer for 'effect' (I have seen 'Vibrato effect ' mean 'tremolo' so perhaps 'effect' could also mean 'tremolo'). I'm not sure about the 'guitarist's' bit.
'lot more rocking' is the wordplay.
'rocking' indicates anagramming the letters.
'lot'+'more'='lotmore'
'lotmore' is an anagram of 'TREMOLO'.
'gets' acts as a link.
Can you help me to learn more?
(Other definitions for tremolo that I've seen before include "Wavering note" , "Vibrato effect" , "Unsteady effect" , "Paganini's effect" , "Quivering effect (in music)" .)