Greek character dealt abroad (5)
I believe the answer is:
delta
'greek character' is the definition.
(letter from the Greek alphabet)
'dealt abroad' is the wordplay.
'abroad' indicates anagramming the letters.
'dealt' with letters rearranged gives 'DELTA'.
(Other definitions for delta that I've seen before include "Triangular patch of land at mouth of river" , "Wing shape; Greek D" , "Extended area at river mouth" , "Eg, outlet of the Nile" , "Silted estuary" .)