It may be delivered by a terse and merciful judge (5,8)

'it may be delivered' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'a terse and merciful judge' is the wordplay.
'a terse' becomes 'short' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'merciful judge' becomes 'sentence' (I've seen this before. I am not sure about the 'merciful' bit.).
'short'+'sentence'='SHORT SENTENCE'

'by' acts as a link.

Can you help me to learn more?