Troublemaker in port starts to turn everyone rebellious (6)
I believe the answer is:
rioter
'troublemaker' is the definition.
(rioter is a kind of troublemaker)
'port starts to turn everyone rebellious' is the wordplay.
'port' becomes 'rio' (I've seen this before).
'starts to' indicates taking the first letters.
The first letters of 'turn everyone rebellious' is 'ter'.
'rio'+'ter'='RIOTER'
'in' is the link.
(Other definitions for rioter that I've seen before include "One involved in civil unrest" , "Troublemaker involved in disturbing the peace" , "One of a crowd involved in wild disturbance" , "Rebel" , "One engaged in a violent disturbance of the peace" .)