Once more select singers for touring across America (8)
I believe the answer is:
reassign
'once more select' is the definition.
('assign' is an answer for 'select' so perhaps 'reassign' is OK for 'once more select')
'singers for touring across america' is the wordplay.
I cannot quite see how this works, but
'america' could be 'a' (common abbreviation - e.g. in organisation names) and 'a' is located in the answer.
an anagram of 'singers' is 'ressign' which is located in the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for reassign that I've seen before include "Move somebody to a different position" , "Freshly allocated" , "Allocate again" , "change duties" , "Give out afresh" .)