Drinkable, not too heavy (8)

I believe the answer is:
portable
This clue might be a double definition.
'drinkable' is the first definition.
Both the definition and answer are adjectives. Perhaps you can see a link between them that I can't see?
'too heavy' is the second definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'not' acts as a link.
Can you help me to learn more?
(Other definitions for portable that I've seen before include "radio" , "easy to bear?" , "Designed to be easily carried" , "Light enough to carry" , "Able to be carried" .)
