London criminal, one going to pot (3,4)
I believe the answer is:
tea leaf
I believe this is a double definition.
'london criminal' is the first definition.
(Cockney rhyming slang for 'thief')
'one going to pot' is the second definition.
(a tea leaf might be put in a tea pot)
(Other definitions for tea leaf that I've seen before include "One from Assam perhaps" , "one exhibiting a fortune?" , "Light-fingered Londoner" , "might be spotted in China" , "One taking" .)