Pattern to trees changes (7)
I believe the answer is:
rosette
'pattern' is the definition.
(I've seen this before)
'to trees changes' is the wordplay.
'changes' is an anagram indicator.
'to'+'trees'='totrees'
'totrees' is an anagram of 'ROSETTE'.
(Other definitions for rosette that I've seen before include "Prize; favour" , "Flower-like badge" , "Ribbon prize or badge" , "Prizewinner's decoration" , "sign of a champion?" .)