Mime artist clutches belly, absorbing one in character (3,6)
I believe the answer is:
air guitar
'mime' is the definition.
(mime of playing an air guitar)
I don't understand how the remainder of the clue works.
(Other definitions for air guitar that I've seen before include "Imaginary instrument played by rock fans!" , "Imaginary instrument that one pretends to play" , "Imaginary stringed instrument" , "Instrumental object that's non-existent" , "Just imagine playing this" .)