Because microphone was universal
I believe the answer is:
cosmic
'universal' is the definition.
(relating to the universe)
'because microphone' is the wordplay.
'because' becomes 'cos' (I've seen this in other clues).
'microphone' becomes 'mic'.
'cos'+'mic'='COSMIC'
'was' acts as a link.
(Other definitions for cosmic that I've seen before include "Large -- universal" , "Great" , "Johann Sebastian --" , "Coming from outer space" , "Of the entire universe" .)