Even rat cooked for old soldier (7)
I believe the answer is:
veteran
'old soldier' is the definition.
(I've seen this before)
'even rat cooked' is the wordplay.
'cooked' is an anagram indicator.
'even'+'rat'='evenrat'
'evenrat' with letters rearranged gives 'VETERAN'.
'for' acts as a link.
(Other definitions for veteran that I've seen before include "Old hand, ex-service person" , "One with lengthy experience in service" , "he's seen a lot of service" , "Nervate (anag.)" , "An old hand or ex-soldier in USA" .)