The style to accommodate a girl, mister! (6)
I believe the answer is:
manner
'the style' is the definition.
('manner' can be a synonym of 'style')
'to accommodate a girl mister' is the wordplay.
'to accommodate' indicates putting letters inside.
'a girl' becomes 'anne' (I've seen this before**).
'mister' becomes 'mr' ('Mr' can be a synonym of 'mister').
'anne' placed within 'mr' is 'MANNER'.
(Other definitions for manner that I've seen before include "Deportment or method" , "Kind, sort" , "Demeanour" , "Way in which something is done" , "Bearing - fashion" .)