Disorganised old citizen retiring after tea (7)
I believe the answer is:
chaotic
'disorganised' is the definition.
('chaotic' can be similar in meaning to 'disorganized')
'old citizen retiring after tea' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'citizen' becomes 'cit' (old-fashioned abbreviation for citizen).
'retiring' says the letters should be written backwards.
'after' means one lot of letters go next to another.
'tea' becomes 'cha' (cha is a type of tea).
'cit' backwards is 'tic'.
'o'+'tic'='otic'
'otic' put after 'cha' is 'CHAOTIC'.
(Other definitions for chaotic that I've seen before include "In a confused state" , "Topsy-turvy" , "Confused and disorderly" , "All over the place" , "In complete disorder" .)