Back in Hanoi, daring to send a message (5)
I believe the answer is:
radio
'send a message' is the definition.
(I've seen this before)
'back in hanoi daring' is the wordplay.
'back' is a reversal indicator.
'in' says the answer is hidden in the clue.
'oidar' is hidden in the letters of 'hanoi daring'.
'oidar' back-to-front is 'RADIO'.
'to' is the link.
(Other definitions for radio that I've seen before include "broadcasting station" , "Wireless broadcast" , "Sound receiver" , "Broadcast receiver" , "Broadcast medium" .)