Possible Clues:

• The Plank produced by director's father taking in gents from the start
• Level the surfer is on tends to be creaky if it's not nailed properly
• Leave clueless directors supporting plank
• River animal trapped in torrent? Plank of wood produced
• Something potential creaky to baffle the bosses?
• Squeak source, at times
• Old roof bar replaced to provide support from below
• One of those building requisites that defeat managers?
• Plank
• Where a foot rests