Having abandoned property plot located round Old Street (4-3-5)
I believe the answer is:
lost-and-found
'having abandoned' is the definition.
I know nothing about this answer so I can't tell whether this works.
'property plot located round old street' is the wordplay.
I cannot really see how this works, but
'property' could be 'tan' (tan is a kind of property) and 'tan' is found within the answer.
'located' could be 'found' (I've seen this in another clue) and 'found' is located in the answer.
'round' could be 'o' (o is a circular letter) and 'o' is found within the answer.
The remaining letters 'lsd' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?