Started with seaman (3)
I believe the answer is:
tar
'seaman' is the definition.
(Jack Tar is an informal term for a sailor)
'started with' is the wordplay.
'with' indicates a hidden word.
'TAR' is hidden in the letters of 'started'.
(Other definitions for tar that I've seen before include "Familiar sailor - what a rat" , "Black liquid from coal" , "Informal sailor or coal distillation" , "Viscous bituminous substance" , "Liquid from wood, coal" .)