let one's short back and sides down

present singular third person lets one's short back and sides down · participle present letting one's short back and sides down

1. informalTo let one's hair down, especially on the part of a man who is very straight-laced.

   Even a military man, though, can let his short back and sides down when national pride is to be celebrated.

   2012, Jeff Dawson, Back Home: England And The 1970 World Cup, →ISBN

   2 more examples

   It's on the way home that they let their hair down.' Well, only as much as you can let short-back-and-sides down.

   2008, Tom Gleeson, Playing Poker with the SAS: A Comedy Tour of Iraq and Afghanistan, →ISBN

   I'd like to see chef Shaun let his short back-and-sides down and serve that sauce over a rolled, braised veal breast, or a veal cheek (there's a pig's cheek on the 10 course menu).

   2013 September 11, Wilfrid, “Juni: Shaun Hergatt's Second Act”, in At the Sign of the Pink Pig