Describe as old and unattractive (7)
I believe the answer is:
explain
'describe' is the definition.
(I've seen this before)
'old and unattractive' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'and' means one lot of letters go next to another.
'unattractive' becomes 'plain' (similar in meaning).
'ex'+'plain'='EXPLAIN'
'as' is the link.
(Other definitions for explain that I've seen before include "Defend" , "Make comprehensible" , "Describe" , "Elucidate, make clear" , "Spell out" .)