Cleaner strand cut by tool, finally (6)
I believe the answer is:
bleach
'cleaner' is the definition.
(I've seen this before)
'strand cut by tool finally' is the wordplay.
'strand' becomes 'beach' (I've seen this before).
'cut by' means one lot of letters goes inside another.
'finally' says to take the final letters.
The final letter of 'tool' is 'l'.
'beach' placed around 'l' is 'BLEACH'.
(Other definitions for bleach that I've seen before include "Whitening chemical" , "Stuff that whitens, hair or cloth" , "Sink and toilet cleaner" , "Purge" , "Peroxide" .)