Seaman? Hardly, yet a safe keeper (9)
I believe the answer is:
custodian
'keeper' is the definition.
(synonyms)
'seaman? hardly yet a safe' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for custodian that I've seen before include "Guardian" , "Protector/guardian (of something)" , "One takes care of" , "museum keeper" , "Protector" .)