Lead-in to center or room

REC

Think of a common prefix for places where you might exercise or gather with others.

This clue plays on the word "rec," which is a common short form for "recreation." It works as a lead-in to words like "center" (as in "rec center") or "room" (as in "rec room"). The trick is recognizing that "rec" isn’t just a standalone word but a prefix often used in everyday phrases for places meant for fun or activities.