Article introducing this country’s seabirds (4)
I believe the answer is:
auks
'seabirds' is the definition.
(auk is a kind of seabird)
'article introducing this country's' is the wordplay.
'introducing' suggests taking the first letters (I've seen 'introduced' mean this).
'this country's' becomes 'UK's' (United Kingdom).
The initial letter of 'article' is 'a'.
'a'+'uks'='AUKS'
(Other definitions for auks that I've seen before include "Birds (such as razorbills)" , "Fliers" , "Northern black and white diving birds" , "Stocky diving birds" , "Sticky diving seabirds" .)