Washing lines reportedly fastened with tags (9)
I believe the answer is:
tidemarks
'washing lines' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps you can see a link between them that I can't see?
'reportedly fastened with tags' is the wordplay.
'reportedly' shows a homophone (sound like).
'fastened' becomes 'tied' (tying is a kind of fastening).
'with' is a charade indicator (letters next to each other).
'tags' becomes 'marks' ('mark' can be a synonym of 'tag').
'tied' is a homophone of 'tide'.
'tide'+'marks'='TIDEMARKS'
Can you help me to learn more?
(Another definition for tidemarks that I've seen is " Indicators of water level".)