The sea urchin is to use chin correctly (7)
I believe the answer is:
echinus
'the sea urchin' is the definition.
(I've seen this in another clue)
'use chin correctly' is the wordplay.
'correctly' indicates an anagram.
'use'+'chin'='usechin'
'usechin' with letters rearranged gives 'ECHINUS'.
'is to' is the link.
(Other definitions for echinus that I've seen before include "Marine creature" , "Sea creature" , "Urchin" .)