Take no notice of the ruin of a region (6)
I believe the answer is:
ignore
'take no notice of' is the definition.
(to take no notice of something is to ignore it)
'ruin of a region' is the wordplay.
'ruin of' indicates an anagram.
'region' anagrammed gives 'IGNORE'.
'the' acts as a link.
(Other definitions for ignore that I've seen before include "bypass" , "Blank" , "Refuse to notice or acknowledge" , "Spurn" , "Forget" .)