Old opponent fairly devoid of it (7)
I believe the answer is:
antique
'old' is the definition.
('antique' can be similar in meaning to 'old')
'opponent fairly devoid of it' is the wordplay.
'opponent' becomes 'anti' (I've seen this before).
'fairly' becomes 'quite' (I've seen this before).
'devoid of' indicates named letters should be taken away.
'quite' with 'it' taken away is 'que'.
'anti'+'que'='ANTIQUE'
(Other definitions for antique that I've seen before include "Object from the past sought by collectors" , "Object valued because of age" , "Object that has acquired value with age" , "Valuable old object" , "from long ago" .)