Start to fill clothes-horse, weather so improved? (6)
I believe the answer is:
fairer
'weather so improved?' is the definition.
(as in fair weather)
'start to fill clothes-horse' is the wordplay.
'start to' suggests taking the first letters.
'clothes-horse' becomes 'airer' (I've seen this before).
The first letter of 'fill' is 'f'.
'f'+'airer'='FAIRER'
(Other definitions for fairer that I've seen before include "Less inclined to show bias" , "Blonder" , "More equitable or blonde" , "More blond or equitable" , "More reasonable" .)