banana skin 
noun
1The skin of a banana, especially when peeled off and discarded: you can compost banana skins, peelings, teabags, and eggshells...
- Rubbing the outsides of banana skins on leather shoes will give them a nice polish because the skins contain potassium, a key ingredient in commercial shoe polish.
- Collect vegetable and fruit waste such as peelings, cores and banana skins in a small kitchen bin.
- Take the half marathon last year for example, there were 80,000 discarded bottles and thousands of dropped banana skins.
1.1British informal Used to refer to a cause of difficulty or embarrassment: the minister was appointed to spot political banana skins this game remains a potential banana skin for Burnley the world’s two major economic powers seem unable to avoid slipping on a banana skin...
- The trade-off of shutting six maternity and A & E departments around the country will also be a political banana skin, particularly with local elections coming up next year.
- ‘The conditions were difficult but credit to the players for doing a professional job,’ said the away manager, who knew the tie had been a potential banana skin.
- If Smith was sensing the vultures circling overhead, he did well to conceal it instead congratulating his team for the way they put outside pressures to one side and avoided a potential banana skin.
From the slapstick convention of falling over as a result of slipping on a discarded banana skin