Gold in trashed mart causes shock (6)
I believe the answer is:
trauma
'shock' is the definition.
(I've seen this before)
'gold in trashed mart' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'in' means one lot of letters goes inside another.
'trashed' indicates anagramming the letters (I've seen this in other clues).
'mart' anagrammed gives 'trma'.
'au' going within 'trma' is 'TRAUMA'.
'causes' acts as a link.
(Other definitions for trauma that I've seen before include "Shock with long-lasting effects" , "Physical injury - powerful emotional shock" , "hurt" , "Wounding shock" , "Physical or mental shock" .)