Old soldiers scared to set off (8)
I believe the answer is:
redcoats
'old soldiers' is the definition.
'scared to set off' is the wordplay.
'set off' is an anagram indicator.
'scared'+'to'='scaredto'
'scaredto' anagrammed gives 'REDCOATS'.
(Other definitions for redcoats that I've seen before include "men who used to fight for Britain" , "Old British soldiers in colourful uniforms" , "British soldiers during the American revolution" .)