Range of colours spread across permit (7)
I believe the answer is:
palette
'range of colours' is the definition.
(I've seen this before)
'spread across permit' is the wordplay.
'spread' becomes 'pate' (pate is a kind of spread**).
'across' is an insertion indicator.
'permit' becomes 'let' ('let' can be a synonym of 'permit').
'pate' enclosing 'let' is 'PALETTE'.
(Other definitions for palette that I've seen before include "Artist's painting board" , "Painter's equipment" , "Variety of tones" , "Artist's paint mixing board" , "Painter's board" .)