Troubled mission for a survey sweeping The Orient (6,8)

'troubled mission' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'a survey sweeping the orient' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'survey' could be 'poll' (polling is a kind of surveying) and 'poll' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'orient' could be 'e' and 'e' is found in the answer.
This explanation may well be incorrect...

'for' acts as a link.

Can you help me to learn more?