Appropriate moment to issue returns (4)
I believe the answer is:
time
'appropriate moment' is the definition.
'time' can be an answer for 'moment' (time is a kind of moment). I'm not sure about the 'appropriate' bit.
'issue returns' is the wordplay.
'issue' becomes 'emit' (both can mean to give out or radiate).
'returns' says the letters should be written backwards.
'emit' reversed gives 'TIME'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for time that I've seen before include "It's done in prison" , "Speech to close pub" , "> moment" , "See 1 and 21" , "It's measured by watch or clock" .)