Cryptic-clue explanation: What does “One in 10?” mean in the definition of ‘Ladle’

The clue in question is

Labour leader entering into deal upset one in 10? (5)

I have solved this via the wordplay but I don’t see how the definition applies.

The answer is 'ladle' (L in (DEAL)) but I don’t get how ‘one in 10?’ defines ladle.

• What was clue 10 in this crossword? Sometimes a number in a crossword clue suggests you need to reference another clue, substituting its answer in for the number...
– Stiv
Mar 21 at 13:23
• Clue 10 is Gruel, so yeah that works out - a ladle is ‘something you might find in gruel’ - with the 10 I guess being some misdirection for 10 Downing Street. Mar 21 at 13:37

I believe you have a situation here where this answer is entirely dependent on the crossword in which it was set - specifically, upon the answer to Clue 10 in the same puzzle, the answer to which is intended to be substituted in to this clue to form part of the wordplay.

A search online suggests that this clue was set as part of the Independent's cryptic crossword on 9 February 2019 (#10086 by Serpent). In this crossword, clue 10A was clued by:

1. Setter catching right bus having lost case for cheap fare (5)

The answer here is GRUEL (cheap fare), from GEL (setter) containing R (right) and _U_ ('BUS' without its 'case' i.e. first and last letters).

Now your clue (23A in the same crossword) makes perfect sense, as 'one in gruel?' would be an acceptable definition for a LADLE, perfectly complementing the wordplay you have already found!

• Yes, that’s it! It was reprinted in the i last Saturday, definitely clue 10. I did wonder why the ‘one’ and ‘10’ were typed out differently. Mar 21 at 13:41
• @LongwellJ Aha, I figured it had to have been reprinted more recently (or you were working your way through a compilation book) - puzzles often get sold across whole families of newspapers after all, and the Independent and the i are sisters so that checks out. Glad I could help!
– Stiv
Mar 21 at 13:44
• @LongwellJ One convention that happens sometimes is they'll use the Arabic number (e.g. 10 in this case) to refer to another clue, and the spelled out number (e.g. "one") to refer to the literal value of 1. Mar 22 at 13:41