Endless banter with line I'm spinning (12)
I believe the answer is:
interminable
'endless' is the definition.
(I've seen this before)
'banter with line i'm spinning' is the wordplay.
'with' says to put letters next to each other.
'spinning' indicates an anagram.
'banter'+'line'+'im'='banterlineim'
'banterlineim' anagrammed gives 'INTERMINABLE'.
(Other definitions for interminable that I've seen before include "Tedious" , "Unending" , "Long drawn-out" , "Without end" , "Seeming likely to go on for ever" .)