Silly fashion upset head of textiles (4)
I believe the answer is:
daft
'silly' is the definition.
(I've seen this before)
'fashion upset head of textiles' is the wordplay.
'fashion' becomes 'fad' (fad is a kind of fashion**).
'upset' shows that the letters should be reversed in order.
'head of' says to take the initial letters.
The first letter of 'textiles' is 't'.
'fad' written backwards gives 'daf'.
'daf'+'t'='DAFT'
(Other definitions for daft that I've seen before include "Barmy, crackers" , "Stupid" , "Idiotic" , "Informally silly or crazy" , "Potty" .)