Take no notice of developing 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)
'developing region' is the wordplay.
'developing' indicates anagramming the letters (letters developed into a new form).
'region' anagrammed gives 'IGNORE'.
(Other definitions for ignore that I've seen before include "Give no attention to" , "Fail to consider" , "Brush off" , "Disregard - cut" , "Slight" .)