Feature of tsar – I establish frontiers (10)
I believe the answer is:
rainforest
'feature' is the definition.
(I have seen 'geographical feature' mean 'rainforest' so perhaps 'feature' could also mean 'rainforest')
'tsar i establish frontiers' is the wordplay.
I cannot really see how this works, but
'i' could be 'a' and 'a' is found within the answer.
an anagram of 'frontiers' is 'rinforest' which is within the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for rainforest that I've seen before include "Luxuriant tropical woodland" , "Luxuriant expanse" , "area of ecological importance" , "Tropical jungle" , "Dense luxuriant tropical zone" .)