People opposed to the enemy are in a rush (4,7,4)
I believe the answer is:
race against time
Here is my best explanation:
'in a rush' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'people opposed to the enemy' is the wordplay.
'people' becomes 'race' (people can mean a national group or race).
'opposed to' becomes 'against' (I've seen this before).
'the enemy' becomes 'time' (the enemy when speaking figuratively).
'race'+'against'+'time'='RACE AGAINST TIME'
'are' acts as a link.