Old soldier or cadet, perhaps (7)
I believe the answer is:
redcoat
'old soldier' is the definition.
(I've seen this before)
'or cadet perhaps' is the wordplay.
'perhaps' indicates an anagram.
'or'+'cadet'='orcadet'
'orcadet' anagrammed gives 'REDCOAT'.
(Other definitions for redcoat that I've seen before include "Do react (anag) - old soldier" , "British soldier (historical)" , "British soldier in the American War of Independence" , "One employed to entertain" , "British soldier (hist.)" .)