Nonsense from Jethro Tull (3)
I believe the answer is:
rot
'nonsense' is the definition.
(rot can mean nonsense or rubbish)
'from jethro tull' is the wordplay.
'from' says the answer is hidden in the clue.
'ROT' is hidden within 'jethro tull'.
(Other definitions for rot that I've seen before include "Decay, moulder" , "Rhubarb" , "Garbage" , "Balderdash" , "Paradise" .)