Better deal on a mortgage, in brief

REFI

Lowering your loan’s rate might involve this four-letter financial shortcut.

This clue is looking for a short term used when someone replaces their current mortgage with a new one to get a lower interest rate or better terms. "Better deal on a mortgage" hints at refinancing, and "in brief" signals the answer is an abbreviation. The common shorthand for refinancing is "REFI," which fits the clue perfectly.