Belittle girl with short skirt? Say nothing! (8)
I believe the answer is:
diminish
'belittle' is the definition.
(synonyms)
'girl with short skirt? say nothing' is the wordplay.
'girl' becomes 'Di'.
'with' says to put letters next to each other.
'short skirt?' becomes 'mini' (I've seen this before).
'say nothing' becomes 'sh' (I've seen this in other clues).
'di'+'mini'+'sh'='DIMINISH'
(Other definitions for diminish that I've seen before include "cut down" , "Make or become smaller" , "Drop" , "Make smaller or less" , "Make less with mini dish" .)