Flan has a new pattern (6)
I believe the answer is:
tartan
'pattern' is the definition.
(I have seen 'Pattern of clan' mean 'tartan' so perhaps 'pattern' could also mean 'tartan')
'flan has a new' is the wordplay.
'flan' becomes 'tart' (I've seen this before).
'has' means one lot of letters go next to another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'tart'+'a'+'n'='TARTAN'
(Other definitions for tartan that I've seen before include "Ship in Mediterranean" , "Pattern of the Scottish clans" , "dress?" , "Cloth with a plaid design" , "Scottish plaid design" .)