Bar allowed female to take up new position (4)

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

Free [allowed] becomes REEF when F (female) takes up a new position. Last Tuesday we had REEF defined as ‘bank’ and Pip commented:  Reef is rock or coral and a bank is sand. I think the same can be said of ‘bar’. REEF defined as ‘bank’ also appeared in The Guardian puzzle last Friday.