Polish female nice Belgian backs (5)
I believe the answer is:
sheen
'polish' is the definition.
(I've seen this in another clue)
'female nice belgian backs' is the wordplay.
'female' becomes 'she' ('she' refers to a woman).
'backs' indicates one should take the final letters (I've seen 'back' mean this).
The last letters of 'nice belgian' are 'en'.
'she'+'en'='SHEEN'
(Other definitions for sheen that I've seen before include "brilliance" , "Sureface shine" , "Acting family" , "Oil slick" , "Glow" .)