Cautious, initially, because distractedly ignoring signs is a danger to seafarers (9)
I believe the answer is:
charybdis
'a danger to seafarers' is the definition.
(mythological sea monster)
'cautious initially because distractedly ignoring signs' is the wordplay.
'cautious' becomes 'chary' (similar in meaning).
'initially' suggests taking the first letters.
The initial letters of 'because distractedly ignoring signs' is 'bdis'.
'chary'+'bdis'='CHARYBDIS'
'is' acts as a link.
(Other definitions for charybdis that I've seen before include "Whirlpool, across from 14" , "Scylla's counterpart" , "monster" , "Mythical whirlpool" , "Whirlpool opposite Scylla" .)