Half past seven in the evening is a time of depression (8-6)

'the evening is a time of depression' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'half past seven' is the wordplay.
'half' becomes 'thirty' (I have seen 'Half of threescore ' mean 'thirty' so perhaps 'half' could also mean 'thirty').
'past' is a charade indicator (letters next to each other).
'seven' becomes 'nineteen' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'thirty' after 'nineteen' is 'NINETEEN-THIRTY'.

'in' acts as a link.

Can you help me to learn more?