Interminable nonsense about on street (8)
I believe the answer is:
constant
'interminable' is the definition.
(thesaurus)
'nonsense about on street' is the wordplay.
'nonsense' becomes 'cant' (cant is a kind of nonsense**).
'about' means one lot of letters goes inside another.
'street' becomes 'st'.
'on'+'st'='onst'
'cant' placed around 'onst' is 'CONSTANT'.
(Other definitions for constant that I've seen before include "Steady and unceasing" , "Stable" , "Changeless and unceasing" , "staying the same" , "Remaining the same" .)