Lighten lingerie originally in maroon (6)
I believe the answer is:
bleach
'lighten' is the definition.
(I've seen this before)
'lingerie originally in maroon' is the wordplay.
'originally' suggests taking the first letters.
'in' indicates putting letters inside.
'maroon' becomes 'beach' (I can't justify this - if you can you should give a lot more credence to this answer).
The initial letter of 'lingerie' is 'l'.
'l' put inside 'beach' is 'BLEACH'.
Can you help me to learn more?
(Other definitions for bleach that I've seen before include "Whitening chemical" , "Get lighter" , "Whiten by sunlight or chemicals" , "Make colourless" , "Disinfectant and whitener" .)