Fizz right up (5)
I believe the answer is:
astir
'up' is the definition.
(I know that up can be written as astir)
'fizz right' is the wordplay.
'fizz' becomes 'asti'.
'right' becomes 'r' (abbreviation).
'asti'+'r'='ASTIR'
(Other definitions for astir that I've seen before include "Starting to move" , "Up and about -- is art (anag)" , "In motion - out of bed" , "Moving; out of bed" , "Excitedly moving" .)