Scream from Port Talbot's leader (4)
I believe the answer is:
riot
'scream' is the definition.
(I've seen this before)
'port talbot's leader' is the wordplay.
'port' becomes 'rio' (I've seen this before).
'leader' indicates taking the first letters.
The initial letter of 'talbot' is 't'.
'rio'+'t'='RIOT'
'from' is the link.
(Other definitions for riot that I've seen before include "Lavish display (of colour)" , "Public disorder" , "Take to the streets" , "Wild disturbance by crowd of people" , "Affray, fighting in the streets" .)