The term 'FIXES UP, AS AN OLD HOUSE' can be summarized by the crossword solution REHABS, which is a 6-letter word. The term refers to the process of renovating an old house, which typically involves repairing and replacing worn out or damaged parts, as well as updating the interior and exterior of the house. This process is often referred to as 'rehabbing' a house, hence the crossword solution REHABS.