Rave organised by North American port stuck in routine (3,4)
I believe the answer is:
run riot
'rave' is the definition.
(both can mean to get out of control)
'north american port stuck in routine' is the wordplay.
'north' becomes 'N' (abbreviation).
'american port' becomes 'Rio' (Rio de Janeiro, port in Brazil in South America).
'stuck in' means one lot of letters goes inside another.
'routine' becomes 'rut' (being stuck in a rut is being stuck in a routine).
'n'+'rio'='nrio'
'nrio' going into 'rut' is 'RUN RIOT'.
'organised by' is the link.
(Other definitions for run riot that I've seen before include "Lose control" , "go crazy" , "Go berserk" , "Of mob, throw off all restraint" , "Behave in unruly way like mob" .)