Clown, possible cause of platform's disintegration? (7)
I believe the answer is:
pierrot
'clown possible cause' is the definition.
'pierrot' can be an answer for 'clown' (I've seen this before). I am not sure about the 'possible cause' bit.
'platform's disintegration?' is the wordplay.
'platform' becomes 'pier' (I have seen 'Coastal platform ' mean 'pier' so perhaps 'platform' could also mean 'pier').
'disintegration?' becomes 'rot' (I've seen this in another clue).
'pier'+'rot'='PIERROT'
'of' acts as a link.
(Other definitions for pierrot that I've seen before include "Clown from French pantomime with white face and costume - tripe or what?" , "Male clown from French pantomime" , "I report on French pantomime clown" , "In French panto, clown with white face and baggy costume" , "French stage character with white face and costume" .)