Hot stuff, colour sergeant with band (3,6)
I believe the answer is:
red pepper
'hot stuff' is the definition.
(hot food)
'colour sergeant with band' is the wordplay.
'colour' becomes 'red' (red is a kind of colour).
'sergeant with band' becomes 'pepper' (Sgt Pepper's Lonely Hearts Club Band-Beatles album).
'red'+'pepper'='RED PEPPER'
(Other definitions for red pepper that I've seen before include "A hot mouthful" , "pungent food" , "Ripe fruit" , "Very hot condiment like cayenne" , "pimiento" .)