Former clubs wear colour no longer in existence (7)
I believe the answer is:
extinct
'no longer in existence' is the definition.
(I've seen this before)
'former clubs wear colour' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'wear' indicates putting letters inside (to wear something is to be covered up by it).
'colour' becomes 'tint' (tint is a kind of colour).
'c' put inside 'tint' is 'tinct'.
'ex'+'tinct'='EXTINCT'
(Other definitions for extinct that I've seen before include "Long gone, like te dinosaur" , "No longer living, like dinosaur" , "No more vital" , "Like a dodo" , "never to be seen again" .)