Don't start song after bit of lovely junk (6)
I believe the answer is:
lumber
'junk' is the definition.
(thesaurus)
'don't start song after bit of lovely' is the wordplay.
'don't start' means to remove the first letter.
'song' becomes 'number' (I've seen this in another clue).
'after' says to put letters next to each other.
'bit of lovely' becomes 'l' (I can't explain this - if you can you should give a lot more credence to this answer).
'number' with its first letter taken away is 'umber'.
'umber' after 'l' is 'LUMBER'.
(Other definitions for lumber that I've seen before include "Unwanted furniture" , "Clumsily move - junk" , "Unwanted, stored goods" , "Move awkwardly - unwanted household items" , "Move in ungainly way" .)