Across the pond, ordering clan its tartan (13)
I believe the answer is:
transatlantic
'across the pond' is the definition.
(I've seen this before)
'ordering clan its tartan' is the wordplay.
'ordering' indicates an anagram.
'clan'+'its'+'tartan'='clanitstartan'
'clanitstartan' anagrammed gives 'TRANSATLANTIC'.
(Other definitions for transatlantic that I've seen before include "From Europe to America" , "Westward from the UK" , "on other side" , "Across the pond" , "Crossing 'the Pond'" .)