Crossword Genius

Understand an old rocker with very little energy at first did nothing (9)

Ross

I believe the answer is:

'did nothing' is the definition.

'understand an old rocker with very little energy at first' is the wordplay.
'understand' becomes 'get' (getting is a kind of understanding).
'an' becomes 'a'.
'old rocker' becomes 'ted'.
'with very little energy' becomes 've' (I can't explain this - if you can you should believe this answer much more).
'at first' means one lot of letters go next to another.
'get'+'a'+'ted'='getated'
'getated' after 've' is 'VEGETATED'.

I've seen this clue in The Guardian.