Issue call-up to rising Greek character (7)
I believe the answer is:
emanate
'issue' is the definition.
(thesaurus)
'call-up to rising greek character' is the wordplay.
'call' becomes 'name' ('name' can be a synonym of 'call'**).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'to rising' shows that the letters should be reversed in order (going up in a down clue).
'greek character' becomes 'eta' (letter from the Greek alphabet).
'name' back-to-front is 'eman'.
'eta' reversed gives 'ate'.
'eman'+'ate'='EMANATE'
(Other definitions for emanate that I've seen before include "Come forth" , "Flow or proceed from" , "spring" , "Issue or spread out from a source" , "Proceed or issue forth" .)