Section remains in band (4)
'band' is the definition.
(sash is a kind of band)
'section remains' is the wordplay.
'section' becomes 's' (legal abbreviation).
'remains' becomes 'ash' (I've seen this before).
's'+'ash'='SASH'
'in' acts as a link.
(Other definitions for sash that I've seen before include "Window frame; silk band" , "Ribbon as a symbol of rank" , "Strip of cloth worn round the waist" , "seen hanging around Miss World?" , "Band of cloth" .)
But I've got no explanation for this one! Could you help me understand?
(Another definition for sass that I've seen is " Cheek".)