Cockney thief (3,4)
I believe the answer is:
tea leaf
'cockney thief' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tea leaf that I've seen before include "Cockney crook" , "Part of plant used to make drink" , "Ingredient of infusion - thief (rhyming slang)" , "might be spotted in China" , "source of drink?" .)