Make an issue of the Met line, possibly (4)
I believe the answer is:
emit
'make an issue of the met line possibly' is the definition.
I can't judge whether this definition defines the answer.
'the met line possibly' is the wordplay.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'met' means one lot of letters go next to another.
'line possibly' becomes 'emi' (I can't justify this - if you can you should give a lot more credence to this answer).
't' put after 'emi' is 'EMIT'.
Can you help me to learn more?
(Other definitions for emit that I've seen before include "Give out (eg light)" , "Discharge - utter" , "shed" , "'Give off, odour say (4)'" , "'Give out, light say (4)'" .)