First start, then finish and transmit (4)
I believe the answer is:
send
'transmit' is the definition.
(synonyms)
'first start then finish' is the wordplay.
'first start' becomes 's' (1st letter of 'start').
'then' means one lot of letters go next to another.
'finish' becomes 'end' (synonyms).
's'+'end'='SEND'
'and' is the link.
(Other definitions for send that I've seen before include "Forward" , "Dispatch by post" , "Transmit (message)" , "Transport" , "Consign" .)