Not a good case for alms? (4,3)

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

'not a good case' is the wordplay.
I cannot really see how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'case' could be 'box' (boxing is a kind of casing) and 'box' is found in the answer.
The remaining letters 'por' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

'for' is the link.

Can you help me to learn more?