Don't notice so much when it's clean (8)
I believe the answer is:
spotless
'it's clean' is the definition.
(similar in meaning)
'don't notice so much' is the wordplay.
I cannot really understand how this works, but
'notice' could be 'spot' (spot can mean to notice or observe) and 'spot' is located in the answer.
The remaining letters 'less' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'when' is the link.
Can you help me to learn more?
(Other definitions for spotless that I've seen before include "Absolutely pure, clean" , "showing no sign of acne?" , "Without blemish" , "Extremely clean" , "Free from blemish" .)