Harp on lace again, rotated to break tempo (9)
I believe the answer is:
'harp on' is the definition.
'again rotated to break tempo' is the wordplay.
'again' becomes 're' (prefix meaning 'again').
'rotated' becomes 'eit' (I am not sure about this - if you are sure you should believe this answer much more).
'to break' means one lot of letters goes inside another (inserted letters break the word apart).
'tempo' becomes 'rate' (I've seen this in another clue).
're' going around 'eit' is 'reite'.
'lace' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for reiterate that I've seen before include "sound twice?" , "show again" , "Emphasise" , "Say it again for tire eater" , "Say again or repeatedly" .)