Boring, boring organ stops (6)
I believe the answer is:
dreary
'boring' is the definition.
('dreary' can be a synonym of 'boring')
'boring organ stops' is the wordplay.
'boring' becomes 'dry'.
'organ' becomes 'ear' (ear is a kind of organ**).
'stops' means one lot of letters goes inside another (to stop can mean to block a gap).
'dry' placed around 'ear' is 'DREARY'.
(Other definitions for dreary that I've seen before include "Dull, tedious" , "Dark" , "Gloomy - dull" , "Overcast" , "Banal" .)