Torch say not heavy (5)
I believe the answer is:
light
This clue is a double definition.
'torch say' is the first definition.
(I know that torch is a type of light)
'not heavy' is the second definition.
('light' is the opposite to 'heavy')
(Other definitions for light that I've seen before include "Illuminate or ignite" , "not profound" , "Moored vessel warning sailors of a hazard" , "Pane of glass" , "Delicate; illuminate" .)