Boatman's origins in the arts reassessed (3)
I believe the answer is:
tar
'boatman's' is the definition.
(tar is an informal term for a sailor)
'origins in the arts reassessed' is the wordplay.
'origins in' says to take the initial letters (the first letter is the origin of the word).
The first letters of 'the arts reassessed' is 'TAR'.
(Other definitions for tar that I've seen before include "Informal sailor, the rat" , "Liquid from wood, coal" , "Cigarette residue - old word for sailor" , "Sailor (colloq.)" , "Informal sailor or coal distillation" .)