Pest returns light-brown, patterned cloth (6)
I believe the answer is:
tartan
'patterned cloth' is the definition.
(I've seen this before)
'pest returns light-brown' is the wordplay.
'pest' becomes 'rat' (rat can mean a nasty person).
'returns' says the letters should be written in reverse.
'light brown' becomes 'tan' (tan is a light brown colour).
'rat' written backwards gives 'tar'.
'tar'+'tan'='TARTAN'
(Other definitions for tartan that I've seen before include "(Fabric with) distinctive checked pattern" , "Pattern of the Scottish clans" , "Scots material" , "Cloth with a crisscross design" , "chequered cloth" .)