Ran through coastal structure erected last month (7)
I believe the answer is:
pierced
'ran through' is the definition.
'coastal structure erected last month' is the wordplay.
'coastal structure' becomes 'pier'.
'erected' is a reversal indicator.
'last month' becomes 'dec'.
'dec' back-to-front is 'ced'.
'pier'+'ced'='PIERCED'
(Other definitions for pierced that I've seen before include "Punctured" , "Run through" , "stabbed" , "Holed" , "Impaled" .)