Lunar vehicle on Sun? Dodgy things here (6)

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

LEM (abbreviation for Lunar Excursion Module = original name of the vehicle used in the Apollo moon landings) + ON + S (Sun = abbreviation for Sunday). Lemon = slang for something that doesn’t work as well as it should = a dodgy thing.