It's late when two extremists send article to Globe - they're sound asleep (4,2,3,5)
I believe the answer is:
dead to the world
'sound asleep' is the definition.
(I've seen this before)
'it's late when two extremists send article to globe' is the wordplay.
I cannot quite see how this works, but
'late' could be 'dead' (similar in meaning) and 'dead' is found within the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
'to' is found in the answer.
'globe' could be 'world' (synonyms) and 'world' is found in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
A single letter 'h' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'they're' is the link.
Can you help me to learn more?
(Other definitions for dead to the world that I've seen before include "Fast asleep" , "Sound asleep; unconscious" , "Sleeping" .)