Came across chest being loaded in commercial area (6)
I believe the answer is:
market
'commercial area' is the definition.
(I've seen this before)
'came across chest being loaded' is the wordplay.
'came across' becomes 'met' ('meet' can be a synonym of 'come across').
'chest' becomes 'ark' (historical term for a chest).
'being loaded' is an insertion indicator.
'met' placed around 'ark' is 'MARKET'.
'in' is the link.
(Other definitions for market that I've seen before include "(Place of) buying and selling" , "Trading centre" , "Offer for sale, demand" , "Try to sell" , "Trading area" .)