One watches Wall of Sound producer tackling a tango (9)
I believe the answer is:
spectator
'one watches' is the definition.
'wall of sound producer tackling a tango' is the wordplay.
'wall of sound producer' becomes 'spector' (Phil Spector).
'tackling' means one lot of letters goes inside another (I've seen this in other clues).
'tango' becomes 't' (phonetic alphabet: alpha, bravo, charlie etc.).
'a'+'t'='at'
'spector' enclosing 'at' is 'SPECTATOR'.
(Other definitions for spectator that I've seen before include "observer" , "Watcher" , "one found at ground?" , "Part of gate" , "weekly magazine?" .)