About to get less fat and more spotless (7)
I believe the answer is:
cleaner
'more spotless' is the definition.
('clean' can be similar in meaning to 'spotless')
'about to get less fat' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa').
'to get' means one lot of letters go next to another.
'less fat' becomes 'leaner' ('lean' can be the opposite of 'fat' so perhaps 'leaner' is reasonable for 'less fat').
'c'+'leaner'='CLEANER'
'and' is the link.
(Other definitions for cleaner that I've seen before include "Chemical agent for removing dirt" , "Eg, launderer, duster" , "Daily help" , "less sleazy?" , "Dirt remover" .)