Unprofitable bottling bit of vodka, on reflection, producing depression (5)

I believe the answer is:
navel
'depression' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'unprofitable bottling bit of vodka on reflection' is the wordplay.
'unprofitable' becomes 'lean' (similar in meaning).
'bottling' indicates putting letters inside (bottling is a kind of containing).
'bit of' says to take the initial letters.
'on reflection' shows that the letters should be reversed in order.
The initial letter of 'vodka' is 'v'.
'lean' enclosing 'v' is 'levan'.
'levan' reversed gives 'NAVEL'.
'producing' is the link.
Can you help me to learn more?
(Other definitions for navel that I've seen before include "Bellybutton" , "Scar on the stomach (for gazing at?)" , "Umbilicus" , "Where the umbilical cord was once attached" , "Something to contemplate" .)
