Country squire's first visionary sent heavenward (5)
I believe the answer is:
syria
'country' is the definition.
(I know that Syria is a country)
'squire's first visionary sent heavenward' is the wordplay.
'squire's first' becomes 's' (1st letter of 'squire').
'visionary' becomes 'airy' (both can mean dream-like or illusory).
'sent heavenward' is a reversal indicator (in a down clue, letters go up).
'airy' backwards is 'yria'.
's'+'yria'='SYRIA'
(Other definitions for syria that I've seen before include "Captain; omit; refuse container" , "Mediterranean republic" , "Asian country" , "Country E. of Lebanon" , "Country bordering Iraq" .)