Complete laser arrangement finds seller (10)
I believe the answer is:
wholesaler
'seller' is the definition.
(I know that wholesaler is a type of seller)
'complete laser arrangement' is the wordplay.
'complete' becomes 'whole' (similar in meaning).
'arrangement' indicates anagramming the letters.
'laser' is an anagram of 'saler'.
'whole'+'saler'='WHOLESALER'
'finds' is the link.
(Other definitions for wholesaler that I've seen before include "Bulk trader" , "One supplying retailers in bulk" , "Merchant" , "Retailer's supplier" , "retailer of large quantities" .)