Snake, say, let pier collapse (7)
I believe the answer is:
reptile
'snake say' is the definition.
(snake is a kind of reptile)
'let pier collapse' is the wordplay.
'collapse' indicates an anagram.
'let'+'pier'='letpier'
'letpier' anagrammed gives 'REPTILE'.
(Other definitions for reptile that I've seen before include "Serpent" , "loathsome type" , "Snake or crocodile, say" , "Snake or croc?" , "Cold-blooded beast" .)