Shock finding uniform inside streetcar, American (6)
I believe the answer is:
Here is my best explanation:
'shock' is the definition.
(I've seen this before)
'uniform inside streetcar american' is the subsidiary indication.
'uniform' becomes 'u' (phonetic alphabet: alpha, bravo, charlie etc.).
'inside' is an insertion indicator.
'streetcar' becomes 'tram' ('tram' can be a synonym of 'streetcar').
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'u' going within 'tram' is 'traum'.
'finding' is the link.
(Other definitions for trauma that I've seen before include "A lasting emotional shock", "Extreme shock", "Shock with long-lasting effects", "Emotional damage", "dreadful shock!", "Emotional shock or physical injury", "Very distressing experience", "Bodily or mental injury", "Injury" and "Emotional upset".)