Surviving Texan shot twin, dismissing victory (6)
I believe the answer is:
extant
'surviving' is the definition.
('extant' can be similar in meaning to 'surviving')
'texan shot twin dismissing victory' is the wordplay.
'shot' is an anagram indicator.
'dismissing' suggests deleting specific letters.
'victory' becomes 'win' (I've seen this before).
'twin' with 'win' taken out is 't'.
'texan' is an anagram of 'extan'.
'extan'+'t'='EXTANT'
(Other definitions for extant that I've seen before include "Still in existence, surviving" , "Currently in existence" , "Still existing, not obsolete" , "Existing, alive" , "Next at being still existing" .)