Cleaner line drawn in sand (6)
I believe the answer is:
bleach
'cleaner' is the definition.
(I've seen this before)
'line drawn in sand' is the wordplay.
I cannot quite see how this works, but
'line' could be 'l' (used when specifying particular lines from a poem) and 'l' is found in the answer.
'sand' could be 'beach' (sand can refer to a sandy beach) and 'beach' is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bleach that I've seen before include "Sink and toilet cleaner" , "Make colourless" , "Blanche" , "Stuff that whitens, hair or cloth" , "Go white" .)