Charlady about to get less fat (7)
I believe the answer is:
cleaner
'charlady' is the definition.
(I've seen this before)
'about to get less fat' is the wordplay.
'about' becomes 'c' (circa).
'to get' says to put letters next to each other.
'less fat' becomes 'leaner' ('lean' can be the opposite of 'fat' so perhaps 'leaner' is reasonable for 'less fat').
'c'+'leaner'='CLEANER'
(Other definitions for cleaner that I've seen before include "Less soiled" , "less sleazy?" , "Char; less dirty" , "More sanitary" , "Maybe Daily" .)