Cheerful Jamaican's first international in cricket ground (6)
I believe the answer is:
jovial
'cheerful' is the definition.
(I've seen this in another clue)
'jamaican's first international in cricket ground' is the wordplay.
'jamaican's first' becomes 'j' (1st letter of 'jamaican').
'international' becomes 'i' (abbreviation eg in IMF).
'in' is an insertion indicator.
'cricket ground' becomes 'oval' (London cricket ground).
'i' inserted into 'oval' is 'ovial'.
'j'+'ovial'='JOVIAL'
(Other definitions for jovial that I've seen before include "Convivial" , "Full of mirth" , "Genial, joyous" , "Cheerful, friendly" , "Hearty and cheerful like Jupiter" .)