Carry money during journey by air (8)
I believe the answer is:
transmit
'air' is the definition.
(synonyms)
'carry money during journey' is the wordplay.
'carry money' becomes 'm' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'during' indicates putting letters inside.
'journey' becomes 'transit' (transit is a kind of journey).
'm' placed within 'transit' is 'TRANSMIT'.
'by' is the link.
Can you help me to learn more?
(Other definitions for transmit that I've seen before include "Pass on (message)" , "Send from one person to another, or broadcast" , "Send from one to another, electronically say" , "Pass on (a disease)" , "Send (a radio message)" .)