My suffix is done to stew
My prefix a distilled brew
My infix is within
My outfix makes 10 out of 10
What am I?
Hold on a sec, allow me a moment to:
RUMINATE!
My suffix is done to stew
Stew can be eaten, i.e. ATE.
My prefix a distilled brew
RUM is a beverage made through a process of distillation.
My infix is within
A synonym of 'within' is merely IN.
My outfix makes 10 out of 10
If something is exceptional, perhaps you would RATE it 10 out of 10...
All together, this gives us:
RUM + IN + ATE, i.e. 'RUMINATE' - a word which can also mean 'to mull something over' (hence the title).