to tell the truth about something you have tried to hide.

I should probably come clean now and admit that I don't really know how to cook at all.

• be soft on someone
• be sold a pup
• be someone's cup of tea
• be someone's department
• be someone's flesh and blood
• be someone's for the asking
• be someone's main squeeze
• be someone's own flesh and blood
• be someone's pigeon
• be someone's strong point
• be someone's strong suit
• be speaking out of both sides of mouth
• be speaking out of both sides of your mouth
• be spick and span
• be spitting in the wind
• be spitting into the wind
• be spoiling for a fight
• be spoilt for choice
• be spoon-fed
• be staring in the face
• be staring someone in the face
• be stark raving mad
• best bet
• best bib and tucker
• best of both worlds