Playing cards, diamonds is what North increasingly lacks (4,3)

'playing' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

'cards diamonds is what north increasingly lacks' is the wordplay.
I cannot quite understand how this works, but
'cards' could be 'pack' and 'pack' is found in the answer.
'diamonds' could be 'ice' (slang term for diamonds) and 'ice' is found in the answer.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?