Make bad blood when reflecting on a quick communication (8)
I believe the answer is:
aerogram
'quick communication' is the definition.
'aerogram' can be an answer for 'communication' (aerogram is a kind of communication). I'm not certain of the 'quick' bit.
'make bad blood when reflecting on a' is the wordplay.
'make bad' becomes 'mar' (I can't justify this - if you can you should give a lot more credence to this answer).
'blood' becomes 'gore' (gore is a kind of blood).
'when reflecting' is a reversal indicator.
'on' is a charade indicator (letters next to each other).
'mar'+'gore'='margore'
'margore' written backwards gives 'erogram'.
'erogram' put after 'a' is 'AEROGRAM'.
Can you help me to learn more?
(Other definitions for aerogram that I've seen before include "old letter from abroad" , "Air letter (US spelling)" .)