Seaman's manipulative art (3)
I believe the answer is:
tar
'seaman's' is the definition.
(Jack Tar is an informal term for a sailor)
'manipulative art' is the wordplay.
'art' anagrams to 'TAR'.
However, I am not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for tar that I've seen before include "used by those who pay to work on deck" , "Pitch; sailor" , "Old salt or liquid from coal" , "Sailor and dressing for roads" , "Smoker's black deposit" .)