Old soldiers flushed out a Scot (8)
I believe the answer is:
redcoats
'old soldiers' is the definition.
'flushed out a scot' is the wordplay.
'flushed' becomes 'red' ('red' can be a synonym of 'flushed').
'out' indicates an anagram.
'a'+'scot'='ascot'
'ascot' anagrammed gives 'coats'.
'red'+'coats'='REDCOATS'
(Other definitions for redcoats that I've seen before include "Old British soldiers in colourful uniforms" , "men who used to fight for Britain" , "British soldiers during the American revolution" .)