Tricolour's first among equals in flags (6)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

First letter of T [ricolour] inserted into PEERS (equals). The surface suggests that the definition is peter = the Blue Peter flag (flown when a ship in port is about to sail), but it may also be as in “peter out” = weaken and fade away = flag.