Partner of older

WISER

Opposite of foolish when paired with age’s advantage.

The clue "Partner of older" plays on the phrase "older and wiser," where "wiser" is the natural companion to "older." It’s a straightforward reference to the common saying, treating "wiser" as the word that pairs with "older" like a partner. The answer isn’t about literal relationships but about the idiomatic link between the two words.