This is healthy food, yet weight increases wildly (6,9)

'increases wildly' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'this is healthy food yet weight' is the wordplay.
I cannot really see how this works, but
'food' could be 'mushroom' (mushroom is a kind of food) and 'mushroom' is present in the answer.
'yet' could be 'but' (synonyms) and 'but' is present in the answer.
'weight' could be 'ton' (unit of weight) and 'ton' is located in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?