Delighted song No. 1 in Estonia, in conclusion (9)
I believe the answer is:
enchanted
'delighted' is the definition.
('enchant' can be a synonym of 'delight')
'song no 1 in estonia in conclusion' is the wordplay.
'song' becomes 'chant' (song sung by a crowd).
'no 1 in estonia' becomes 'e' (1st letter of 'estonia').
'in' indicates putting letters inside.
'conclusion' becomes 'end' (something's conclusion is its end).
'chant'+'e'='chante'
'chante' inserted within 'end' is 'ENCHANTED'.
(Other definitions for enchanted that I've seen before include "delighted by spelling" , "Beguiled" , "Captivated" , "Delighted, charmed" , "Put under spell" .)