Terrible row with aged lady (7)
I believe the answer is:
dowager
'lady' is the definition.
(I have seen 'old lady' mean 'dowager' so perhaps 'lady' could also mean 'dowager')
'terrible row with aged' is the wordplay.
'terrible' indicates an anagram.
'with' means one lot of letters go next to another.
'row' put after 'aged' is 'agedrow'.
'agedrow' anagrammed gives 'DOWAGER'.
(Other definitions for dowager that I've seen before include "Woman who holds title from dead husband" , "Widow inheriting husband's title or property" , "woman of property?" , "Widow, imposing elderly woman" , "One of 16 [OLD GIRLS]" .)