Angry outburst from one stuck in traffic (6)
I believe the answer is:
tirade
'angry outburst' is the definition.
(I've seen this before)
'one stuck in traffic' is the wordplay.
'one' becomes 'i' (Roman numeral).
'stuck in' is an insertion indicator.
'traffic' becomes 'trade' (I've seen this before).
'i' going inside 'trade' is 'TIRADE'.
'from' acts as a link.
(Other definitions for tirade that I've seen before include "Intemperate outburst" , "Loud harangue" , "Inclination; fish" , "Blast of criticism" , "Erode or melt (material)" .)