Regular orbit of European returning from adversaries (6)
I believe the answer is:
rivals
'adversaries' is the definition.
(I've seen this in another clue)
'regular orbit of european returning' is the wordplay.
'regular' means one should take alternating letters.
'of european' becomes 'slav' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'returning' says the letters should be written in reverse.
The alternate letters of 'orbit' are 'ri'.
'slav' in reverse letter order is 'vals'.
'ri'+'vals'='RIVALS'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for rivals that I've seen before include "Persons in competition with each other" , "Competitors, challengers" , "Opposing contestants" , "Play by 1" , "Opponents or competitors" .)