Capital in Haiti, oddly, and also a European island once! (8)
I believe the answer is:
hibernia
'a european island once' is the definition.
(Latin name for Ireland)
'capital in haiti oddly and also' is the wordplay.
'capital' becomes 'bern' (capital of Switzerland).
'in' means one lot of letters goes inside another.
'oddly' means one should take alternating letters (letters in odd-numbered positions).
'and' says to put letters next to each other.
'also' becomes 'a' (this could be a standard abbreviation of which I'm unaware).
The alternate letters of 'haiti' are 'hii'.
'bern' placed into 'hii' is 'hiberni'.
'hiberni'+'a'='HIBERNIA'
Can you help me to learn more?
(Other definitions for hibernia that I've seen before include "Emerald Isle, historically, poetically" , "Ancient Ireland" , "Poetic name for Ireland, now archaic" , "Latin name for Ireland" , "land once" .)