He sets sails (5)
I believe the answer is:
silas
'he' is the definition.
'sets sails' is the wordplay.
'sets' indicates anagramming the letters (I've seen 'set' mean this (instruction to set the letters)).
'sails' is an anagram of 'SILAS'.
(Other definitions for silas that I've seen before include "Uncle - (Le Fanu); - Marner (Eliot)" , "Weaver" , "Chap" , "-- Wegg (Dickens, OMF)" , "'Uncle . . . . .' , novel by J Sheridan Le Fanu" .)