Area isn't developed well? (8)
I believe the answer is:
artesian
'well?' is the definition.
(artesian well is a kind of well)
'area isn't developed' is the wordplay.
'developed' indicates anagramming the letters.
'area'+'isnt'='areaisnt'
'areaisnt' anagrammed gives 'ARTESIAN'.
(Other definitions for artesian that I've seen before include "This well is bored vertically into the ground" , "(Well) fed by pressure" , "A nastier sort of well, oddly" , "(Well) flowing under natural pressure" , "Type of well that doesn't need a pump" .)