Line round bath reportedly drawn by man (8)
I believe the answer is:
tidemark
'line round bath' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'reportedly drawn by man' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'drawn' becomes 'tied' ('tie' can be a synonym of 'draw').
'by man' becomes 'mark' (I am not sure about the 'by' bit.).
'tied' sounds like 'tide'.
'tide'+'mark'='TIDEMARK'
Can you help me to learn more?
(Other definitions for tidemark that I've seen before include "Dirt around bath" , "washing-line" , "shows extent of clean-up" , "Grimy line round the inside of a bath" , "line on beach" .)