Prevent large city building (5)
I believe the answer is:
block
'prevent' is the definition.
(blocking is a kind of preventing)
'large city building' is the wordplay.
I cannot quite understand how this works, but
'large' could be 'l' and 'l' is present in the answer.
The remaining letters 'bock' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for block that I've seen before include "Jam" , "Cube" , "Solid shape; prevent" , "cake?" , "Mass of wood etc - set of buildings" .)