Disaster with area hit hard in major town (8)
I believe the answer is:
calamity
'disaster' is the definition.
(I know that disaster can be written as calamity)
'area hit hard in major town' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'hit hard' becomes 'lam' (to 'lam' means to hit hard).
'in' is an insertion indicator.
'major town' becomes 'city' (a city is a major settlement).
'a'+'lam'='alam'
'alam' going into 'city' is 'CALAMITY'.
'with' acts as a link.
(Other definitions for calamity that I've seen before include "Musical set in Deadwood" , "A sad or disastrous happening" , "Damaging event" , "15 [JANE] the frontierswoman" , "Disaster, sudden great misfortune" .)