Nonsense written about Laurel originally having three parts (6)
I believe the answer is:
triple
'having three parts' is the definition.
'nonsense written about laurel originally' is the wordplay.
'nonsense' becomes 'tripe' (I've seen this before).
'written about' is an insertion indicator.
'originally' says to take the initial letters.
The initial letter of 'laurel' is 'l'.
'tripe' placed around 'l' is 'TRIPLE'.
(Other definitions for triple that I've seen before include "Consisting of three" , "make score sixty?" , "make much longer" , "Multiply by three" , "involving several parties" .)