Eventually popular issue comes up (2,4)
I believe the answer is:
in time
'eventually' is the definition.
('in time' can be a synonym of 'eventually')
'popular issue comes up' is the wordplay.
'popular' becomes 'in'.
'issue' becomes 'emit' (I've seen this before).
'comes up' says the letters should be written backwards.
'emit' back-to-front is 'time'.
'in'+'time'='IN TIME'
(Other definitions for in time that I've seen before include "Early enough" , "Later perhaps" , "eventually" , "What an orchestra should be" , "not too late" .)