Think again since order goes out (10)
I believe the answer is:
reconsider
'think again' is the definition.
('consider' is an answer for 'think' so perhaps 'reconsider' is OK for 'think again')
'since order goes out' is the wordplay.
'goes out' indicates an anagram.
'since'+'order'='sinceorder'
'sinceorder' with letters rearranged gives 'RECONSIDER'.
(Other definitions for reconsider that I've seen before include "Have second thoughts" , "Think again" , "Ponder further" , "Nice orders ( anag.)" .)