Island producing whisky first of all (5)
I believe the answer is:
malta
'island' is the definition.
(I know that Malta is a island)
'whisky first of all' is the wordplay.
'whisky' becomes 'malt' (malt whisky is a kind of whisky).
'first of all' becomes 'a' (1st letter of 'all').
'malt'+'a'='MALTA'
'producing' acts as a link.
(Other definitions for malta that I've seen before include "Island member of the European Union" , "Mediterranean island state" , "A Med. island" , "detached dwelling place" , "Mediterranean island awarded the George Cross" .)