on the side
on the side {adv. phr.}, {informal}
1. In addition to a main thing, amount or quantity; extra.
He ordered a hamburger with onions and French fries on the side.
His job at the hospital did not pay much, so he found another on the side.
The cowboys in the rodeo competed for prize money and also made bets on the side.
2. or on the --- side
Tending toward; rather.
Grandmother thought Jane's new skirt was on the short side.
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Source: A Dictionary of American Idioms