Prior to climbing a stratovolcano (4)
I believe the answer is:
etna
'prior' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'climbing a stratovolcano' is the wordplay.
'climbing' says the letters should be written backwards (in a down clue, letters climb up).
'a' becomes 'an'.
'stratovolcano' becomes 'te' (I can't justify this - if you can you should believe this answer much more).
'an'+'te'='ante'
'ante' written backwards gives 'ETNA'.
'to' is the link.
Can you help me to learn more?
(Other definitions for etna that I've seen before include "Italian volcano" , "Neat class of volcano in Sicily" , "Europe's highest active volcano" , "feature spewing lava" , "Neat (anag)" .)