Security measure upset travel beyond Driffield following evacuation, by gum! (5,3)
I believe the answer is:
guard dog
'beyond driffield following evacuation by gum' is the definition.
I can't judge whether this defines the answer.
'security measure upset travel' is the wordplay.
'security' becomes 'guard' (I've seen this in another clue).
'measure' becomes 'd' (D is an example).
'upset' says the letters should be written backwards.
'travel' becomes 'go' (synonyms).
'go' in reverse letter order is 'og'.
'guard'+'d'+'og'='GUARD DOG'
Can you help me to learn more?
(Other definitions for guard dog that I've seen before include "Task for an Alsatian" , "Animal protecting property" , "Alsatian, perhaps" , "Canine sentry" , "Its bite should be as good as its bark" .)