Cilla, we're told, is dangerous to sailors (6)
I believe the answer is:
scylla
'dangerous to sailors' is the definition.
I can't judge whether this definition defines the answer.
'cilla we're told' is the wordplay.
'we're told' shows a homophone (sound like).
'cilla' is a homophone of 'SCYLLA'.
'is' is the link.
Can you help me to learn more?
(Other definitions for scylla that I've seen before include "Mythical rock" , "Six-headed monster who sat on a rock opposite Charybdis" , "Artificial cave" , "Charybdis counterpart" , "In Greek myth, sea monster who lived in cave opposite whirlpool Charybdis" .)