Such a blow, with touch of calamity, could result in this shock defeat (3,4,2,5)

'such a blow' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'touch of calamity could result in this shock defeat' is the wordplay.
I cannot really understand how this works, but
'touch' could be 'kiss' (kiss is a kind of touch) and 'kiss' is found in the answer.
'of' could be 'o' and 'o' is located in the answer.
an anagram of 'defeat' is 'efdeat' which is located in the remaining letters.
This may be the basis of clue (or it may be nonsense).

'with' is the link.

Can you help me to learn more?