Is mail organised, writer finally corresponding? (7)
I believe the answer is:
similar
'corresponding?' is the definition.
(similar in meaning)
'is mail organised writer finally' is the wordplay.
'organised' is an anagram indicator.
'finally' says to take the final letters.
The final letter of 'writer' is 'r'.
'is'+'mail'='ismail'
'ismail' with letters rearranged gives 'simila'.
'simila'+'r'='SIMILAR'
(Other definitions for similar that I've seen before include "Of the same kind" , "Appearing the same" , "Comparable" , "Alike, resembling" , "Having a close resemblance to" .)