Take turns that might lead to Etna? (9)
I believe the answer is:
alternate
'take turns' is the definition.
('alternate' can be a synonym of 'take turns')
I cannot understand how the remainder of the clue works.
(Other definitions for alternate that I've seen before include "Change from one thing to another by turns" , "Take turns" , "Change repeatedly between two" , "Change to first the one, then the other" , "Happening or following in turns, one after the other" .)