Second part of song rocked (5)
I believe the answer is:
shook
'rocked' is the definition.
(I've seen this before)
'second part of song' is the wordplay.
I cannot quite see how this works, but
'second' could be 's' (common abbreviation) and 's' is present in the answer.
'part' could be 'hook' (hook is a kind of part) and 'hook' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for shook that I've seen before include "Rocked" , "Trembled, vibrated" , "Shivered" .)