A general style underpins laundry (10)
I believe the answer is:
washington
'a general' is the definition.
(I know that Washington is a general)
'style underpins laundry' is the wordplay.
'style' becomes 'ton' (term for style or fashion).
'underpins' means one lot of letters go next to another (in a down clue, some letters go underneath others).
'laundry' becomes 'washing' (I've seen this before).
'ton' put after 'washing' is 'WASHINGTON'.
(Other definitions for washington that I've seen before include "Seattle's state" , "State - capital - president" , "Tree feller of myth" , "US capital" , "First US president" .)