Mark populated area where there's a shortage (8)
I believe the answer is:
scarcity
'there's a shortage' is the definition.
(I've seen this before)
'mark populated area' is the wordplay.
'mark' becomes 'scar' (mark left by an injury).
'populated area' becomes 'city' (city is a kind of area. I am not sure about the 'populated' bit.).
'scar'+'city'='SCARCITY'
'where' is the link.
Can you help me to learn more?
(Other definitions for scarcity that I've seen before include "Something uncommon" , "Shortage" , "Shortness of supply" , "Inadequate supply" , "Thinness" .)